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B raz i l i an Sy n c h ro tro n Li gh t Labo rato ry

AC T IV IT Y R E PO RT 2 0 1 1

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LNLS ACTIVITY REPORT 2011 Editor Angelo Malachias Management Claudia Izique Proofreader Beatrice Allain The editors express their gratitude to the LNLS users and staff for their contributions, advice and patience. DISCLAIMER This document was prepared as an account of work done by LNLS users and staff. Whilst the document is believed to contain correct information, neither LNLS nor any of its employees make any warranty, expresses, implies or assumes any legal responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed within. As well, the use of this material does not infringe any privately owned copyrights. LNLS Campus Giuseppe Máximo Scolfaro Street, 10.000, Campinas, São Paulo, Brazil Correspondence P.O. Box 6192 Postal Code 13083-970, Campinas, São Paulo, Brazil Telephone +55 19 3512-1010 Fax +55 19 3512-1004 e-mail secre@lnls.br home page www.lnls.br A non-profit organization Brazilian Association for Synchrotron Light Technology (ABTLuS) operate the Brazilian Syncrotron Light Laboratory (LNLS)for the Brazilian Ministry of Science and Technology.

ABTLuS Brazilian Association for Synchrotron Light Technology Director General: Rogério Cezar de Cerqueira Leite (January to June, 2010 – pro tempore) Walter Colli (June to December, 2010) LNLS Brazilian Synchrotron Light Laboratory Director: Antonio José Roque da Silva LNBio Brazilian Biosciences National Laboratory Director: Kleber Gomes Franchini CTBE Brazilian Bioethanol Science and Technology Laboratory Director: Marco Aurélio Pinheiro Lima

Activity Report 2011: LNLS / Brazilian Synchrotron Light Laboratory - Campinas, SP: Brazilian Ministry of Science and Technology / Brazilian Association for Synchrotron Light Technology, 2011. Annual ISSN 1518-0204 1. Synchrotron accelerator. I. LNLS / Brazilian Synchrotron Light Laboratory CDD 539.735

This publication is available at the eletronic format in www.lnls.br/publicacoes

Desktop publishing


Summary

  6  11  95 128

Introduction

Science Highlights Facility Reports

Scientific Reports


INTRODUCTION

Welcome

We are writing this introduction in the middle of 2012 so we are using this opportunity not only to describe the achievements of 2011 but also to provide some recent news that are important for the laboratory. As part of the restructuring that started in 2009, the C2Nano laboratory is now a separate National lab, LNNano, independent from LNLS. With this change, LNLS and the other three National Laboratories: LNBio, LNNano and CTBE now compose the CNPEM (Center for Research on Energy and Materials). Since August 2011, the Director General of CNPEM is Carlos Alberto Aragão de Carvalho Filho. As part of this reorganization, we have built between 2011 and 2012 the main building of LNLS, which now hosts the Scientific Division, the Accelerator Division and the internal management of LNLS. It is located next to the ring, being directly connected to it. Moreover, the chemistry laboratories have been moved there to facilitate the preparation of samples by the users. We have also a new website. So far it is only in English. Both the Portuguese version, as well as further improvements are underway. During the years 2011-2012, we have been dealing with two tasks: • Continuing to maintain and develop the existing facilities of the current 1.37 GeV storage ring; • Reorganize LNLS to face the new challenge for the laboratory: the construction of the 3 GeV new synchrotron radiation source.

THE UVX Storage Ring and Beamlines

Moving from a 1.37 GeV machine with an emittance of 100 nm.rad to a 3 GeV-280 pm.rad one is a very big step. We need to offer to the Brazilian community few beamlines that are competitive at the international level during the construction period of the new source. This is only possible by compensating the large emittance and the low energy of the ring by state of the art equipments at the end-stations of some of the beamlines: these will be moved later on to SIRIUS. Few examples: • It took more than 5 years to build in house the PGM beamline (1001500 eV) based on an EPU undulator (allowing circular and linear polarizations) and a very good monochromator (resolution>15000): it is competitive with similar beamlines existing at 3rd generation facilities. We still need to improve the experimental end-stations: at the end of 2013 we should have a modern ARPES (angle resolved photoemission) setup, a high resolution PEEM (photoemission microscope, 5nm resolution) and a high-field, low temperature, dichroism setup with modern sample preparations facilities. The branch for atomic and molecular science has

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INTRODUCTION

a Scienta analyzer with a setup allowing working on liquid or gases until 1 mbar pressure: some nice results have been obtained recently. The protein crystallography MX2 beamline has been modernized by installing a robot [G-rob system  (NatXray)] allowing automated mounting of cryo-protected crystals as well as crystallization plates. The commissioning took much longer than expected, but the system is operational since October 2011. In the middle of 2011, due to large instabilities in the beamline optics, we have decided to stop the XRD1 beamline to install new optical elements on separate large concrete blocks, as it was previously done on the PGM beamline. This has given quite good results and we will install at the end of 2012 a very competitive powder diffraction set-up including a 3-circle diffractometer with 24 Mythen detectors, a robotic arm, a sample carrousel, a cryojet (80/500K) and a hot air blower (300/1273 K). The commissioning of the 4T wiggler beamline should have started at the beginning of 2011 but was delayed by one year due to a very late delivery of the main mirror (one year). After facing some strong outgasing of the graphite filters and some instabilities of the monochromator, the beamline is having the first users and for the first time at LNLS experiments at 28 keV have been performed. We have decided to build two new beamlines in areas that are booming at 3rd generation facilities: an infrared beamline (imaging and spectroscopy) and a X-Ray imaging beamline. The choice was due to scientific reasons but also to the fact that these beamlines are very cheap compared to other SR beamlines. The goal was to build them in less than 2 years, as a test for the future SIRIUS beamlines. The X-ray imaging beamline is under commissioning now and we hope to reach 1-2 μm resolution. The IR beamline is original in the sense that it couples an AFM (atomic force microscope) to an interferometer (until now this has not been done on a synchrotron). It should allow reaching a spatial resolution of 100 nm at 10 μm, as demonstrated with a thermal source. However the thermal source is fine to do microscopy and spectroscopy on semiconductors and insulators but it is too weak for studying polymers or biological materials. The interferometer and the AFM have been tested and the beamline is under construction and should be installed during the shutdown at the end of 2012.

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INTRODUCTION

• In 2010-2011, the XAFS1 control and data acquisition was changed and modernized successfully (allowing to use EPICS, as is also planned for the future machine). We did the same thing for other 3 beamlines in 2012 and we will do it for other 6 in 2013 The year of 2011 for the Accelerator Division were marked by some small scale modifications of the light source aiming at improving both beam characteristics and operation conditions. Efforts have been made to increase the brightness of the photon beam delivered to the beamlines by reducing the vertical coupling of the beam. Modifications in the accelerator systems have been implemented in order to improve the injection and ramping processes. A new dipole vacuum chamber was designed, built and installed for the new infrared beamline that will use the radiation emitted from one of the dipoles. The emergence of the project for the new third generation light source SIRIUS brought about a whole set of studies and developments focused on the design and specification of the various systems of the new machine. The reliability of the light source was 97.6% (compared to 97.8% in 2010) but we should mention that a large fraction of the losses are due to transient faults of the electricity furnished by CPFL, the energy company provider. We expect an improvement in 2013 because we will be linked to a new, shorter and more direct power line. As you can see in the papers selected for the report, the quality of the research is improving (especially in biology) and we have to continue in that direction.

SIRIUS: THE NEW 3 GeV SOURCE

In the last 4 years, the laboratory has been working on a 3 GeV source to replace the existing one. The design had a target emittance of 2.7 nm.rad and uses permanent magnets dipoles. Several prototypes of the magnets and vacuum chambers have been built and tested. During the first meeting of the Sirius Machine Advisory Committee it was strongly recommended to review the specifications of the storage ring in order to assure that the new synchrotron light source will be a state of the art equipment ten years after its inauguration. This challenge was taken and a new lattice, with 5-bend achromatic cells and emittance of 280 pm∙rad. In addition, 13 beamlines are now included in the budget plan. Our objective is to cover the range 10 eV to 100 keV with undulators and wigglers. The ground breaking will take place in 2013, on a new site next to the actual CNPEM campus. We have started to work on the conceptual design of the first beamlines with the objective to have the PDR (Preliminary Design Report) ready in the second semester of 2013 to start their construction.

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INTRODUCTION

It is never too much to stress that all these achievements would not be possible without the dedication and high quality of the LNLS staff. Antonio JosĂŠ Roque da Silva Director Yves Petroff Scientific Director Harry Westfahl Jr. Deputy Scientific Director Ruy Hanazaki do Amaral Farias Coordinator of the Engineering and Accelerators Division Antonio Ricardo Droher Rodrigues Coordinator of the Sirius Technical Project

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Science Highlights

 12 NMR and 1.0 Å X-Ray determinations of the structure of the VirB7 subunit of Xanthomoas citri.subsp.citri (citrus canker) and its interaction with virB9

 18 The Crystal Complex of Phosphofructokinase-2 of Escherichia coli with Fructose-6-phospate

 25 Macromolecular assembly of polycystin-2 intracytosolic C-terminal domain

 32 Glutaminase C as key for the glutamine-based metabolism of cancer cells

 36 Ferm Domain interaction with myosin negatively regulates FAK in  41  45  51  55  60  65  70  75  79

cardiomyocyte hypertrophy

Bactericidal silver nanoparticles: enhancing biological activity Palladium cools nickel phosphide synthesis

How the new iron-based superconductors work

DNA nucleobases may survive in outer space for billion of years

On the stabilization of gold nanoparticles over silica-based magnetic supports modified with organosilanes Sputtering onto liquids: from thin films to nanoparticles Magnetic thin films

Electrochemical sensing with carbon nanotubes

Synchrotron Radiation X-Ray Microfluorescence Reveals Polarized Distribution of Atomic Elements during Differentiation of Pluripotent Stem Cells

 84 New improvements on silica-supported ceria  89 New data about a promising spintronic material


1

NMR and 1.0 Å X-Ray determinations of the structure of the VirB7 subunit of Xanthomoas citri.subsp. citri (citrus canker) and its interaction with virB9

Diorge P. Souza1, Maxuel O. Andrade1, Cristina E. Alvarez-Martinez1, Guilherme M. Arantes1, Chuck S. Farah1* and Roberto K. Salinas1*

Department of Biochemistry, Institute of Chemistry, University of São Paulo

1

NMR and X-ray models of VirB7XAC2622.

Facilities: MX2 e NMR Publication: PLoS Pathogens (2011) Volume 7 | Issue 5 | e1002031 Funding: FAPESP, CNPq and Capes Corresponding author: Roberto K. Salinas - roberto@iq.usp.br Chuck S. Farah. Phone - chsfarah@iq.usp.br

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NMR and 1.0 Å X-Ray determinations of the structure of the VirB7 subunit of Xanthomoas citri.subsp.citri (citrus canker) and its interaction with virB9

Citrus canker is a desease caused by the phylopathogens Xanthomonas citri subsp. citri, Xanthomonas fuscans subsp. aurantifolli and Xanthomonas alfafae subsp. citrumelonis. Many aspects of bacterial life require the translocation of proteins to the cell exterior. To do this, different macromolecular secretion systems of varying complexity have evolved (Type I-VI secretion systems). the authors have determined the structure (by NMR and X-ray) and studied the interactions of an unusually large VirB7 subunit (VirB7XAC2622) of the outer membrane pore of the Type IV secretion system found in the Xanthomonas genera of phytopathogens.

Citrus canker is a desease caused by the phylopathogens Xanthomonas citri subsp. citri, Xanthomonas fuscans subsp. aurantifolli and Xanthomonas alfafae subsp. citrumelonis. The first of the three species is the most widely spread and severe, attacking all citrus species. In Brazil, this species is the most important, being found in practically all areas where citrus canker has been detected. Like most phytobacterioses, there is no efficient way to control citrus canker. Many aspects of bacterial life require the translocation of proteins to the cell exterior. To do this, different macromolecular secretion systems of varying complexity have evolved (Type I-VI secretion systems). These secretion systems are often at the front lines of pathogen-host interactions and are important for the development of disease. In this work, the authors have determined the structure (by NMR and X-ray) and studied the interactions of an unusually large VirB7 subunit (VirB7XAC2622) of the outer membrane pore of the Type IV secretion system found in the Xanthomonas genera of phytopathogens. Type IV secretion systems (T4SS) are used by Gram-negative bacteria to translocate protein and DNA substrates across the cell envelope and into target cells. Translocation across the outer membrane is achieved via a ringed tetradecameric outer membrane comlex made up of small VirB7 lipoprotein and the C-terminal domains of VirB9 and VirB10 subunits. Its mosaic structure combines a canonical VirB7 N-terminal region with a C-terminal globular domain whose topology is observed in a relatively limited set of proteins, all involved in molecular transport across outer membranes. The results lead to the hypothesis that the VirB7XAC2622 globular domains can form an extra ring around the perimeter of the outer membrane pore and reveal deeper structural and evolutionary relationships among bacterial macromolecular secretion systems that have evolved to adopt a variety

of functions, including structural modules in outer membrane pores (secretins from Type II, III and IV secretion systems, Type IV pili and filamentous phages), signal-transduction modules in TonBdependent receptors and membrane-penetrating devices in T6SS and long-tailed bacteriophages.

Results Solution and Crystal Structures of XAC VirB7 The NMR solution structure consists of a globular domain (residues 52-133), flanked by a long disordered N-terminus (amino acids 24-51) and a short flexible C-terminus (residues 134-139) (Figure 1A). The globular domain is composed of two α-helices sandwiched between a mixed three stranded β-sheet on one side and an antiparallel two-stranded β-sheet plus a short 310 helix on the other (Figure 1B). The NMR structures were independently validated by 1 H-15N residual dipolar couplings (RDCs). To better characterize the globular domain, the authors cloned and purified a recombinant fragment encompassing residues 51-134. VirB7XAC2622_51-134 crystals belong to space group C2221 and diffracted up to 1.0 Å. As expected, the crystal and solution structures are very similar (Figures 1C and 1D), displaying an average root mean square deviation (RMSD) for all heavy atoms of 1.61 ± 0.06 Å for residues 53-130, and excellent agreement with the backbone 1H-15N RDCs [Q factor of 0.187 (regular secondary structures only) and 0.272 (all residues)].

VirB7 Oligomerization Changes in 15N heteronuclear single-quantum coherence (15N-HSQC) cross-peak positions as a function of protein concentration indicated that VirB7XAC2622 oligomerizes in fast exchange on the NMR time scale (Figure 2A).

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SCIENCE HIGHLIGHTS

(A)

(B)

(C)

(D)

Figure 1. NMR and X-ray models of VirB7XAC2622. Superposition of 20 lowest energy VirB7XAC2622_24-139 solution structures: (A) backbone traces of the full-length protein (residues 24-139) (B) ribbon representation of the folded domain (residues 51-134) in the NMR ensemble. (C) Ribbon representation of the X-ray crystal structure of VirB7XAC2622_51-134. Water molecules and one isopropanol ligand are depicted. (D) Superposition of the X-ray (green) and NMR (lowest energy model; red) structures of the VirB7XAC2622 globular domain.

Chemical shift perturbation data showed that two regions are involved in VirB7XAC2622 self-interactions: a region in the unfolded N-terminus (residues 42-49) and a patch on the surface of the globular domain made up of residues 63-65, 85-93, 111-119 and 131 (Figure 2B and C). These observations suggest a headto-tail arrangement where the N-terminus of one molecule recognizes the folded domain of the other. This hypothesis was corroborated by the analysis of a set of 13 NOEs not assigned by CYANA derived from amino acids whose main-chain 1H-15N chemical shifts are perturbed in a concentration dependent manner. This set of 13 intermolecular NOEs were used as geometric restraints to drive computational docking simulations of the VirB7XAC2622 dimer using

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HADDOCK2.0 to determine the general nature of the oligomerization interface (Figure 2D).

VirB7XAC2622 Interaction with VirB9XAC2620

VirB7XAC2622 was previously shown to interact with the C-terminal domain of VirB9XAC2620. The authors therefore produced a fragment, VirB9XAC2620_154-255, corresponding to the C-terminal domain of VirB9XAC2620. Changes in the 15N-HSQC spectrum of VirB7XAC2622_24-139 upon adding VirB9XAC2620_154-255 showed that the binding occurs in slow exchange on the NMR time scale. In order to map the VirB9 binding site on the structure of VirB7, they assigned the backbone resonances of VirB7 XAC2622_24-139 in complex with VirB9XAC2620_154-255 and analyzed the chemical shift differences (Figure 3A and B).


NMR and 1.0 Å X-Ray determinations of the structure of the VirB7 subunit of Xanthomoas citri.subsp.citri (citrus canker) and its interaction with virB9

Figure 2: VirB7XAC2622_24-139 oligomerization. (A) Superposition of 15N-HSQC spectra of 15N-VirB7XAC2622_24-139 at different concentrations. Cyan: 850 µM; blue: 600 µM; green: 400 µM; yellow: 300 µM; orange: 200 µM; pink: 100 µM; red: 50 µM; purple: 25 µM; brown: 13 µM and black: 7 µM. (B) Weighted chemical shift changes (∆δcomp) observed upon dilution from 100 µM to 7 µM. (C) Surface representation of VirB7XAC2622_24-139 colored according to the weighted chemical shift changes. (D) Ribbon representations of docking models of the VirB7XAC2622 – VirB7XAC2622 interaction. Residues involved in intermolecular NOEs (nuclear Overhauser effect) are shown as stick models colored brown.

This analysis showed that only residues 27-41, within the disordered VirB7 N-terminus, undergo significant chemical shift perturbations (Figure 3C and D). This region is adjacent to, but does not overlap, the N-terminal region involved in VirB7XAC2622 oligomerization (residues 42-49).

Discussion

The structure of the outer membrane complex of the T4SS coded by the conjugative E. coli plasmid pKM101 has been determined by X-ray crystallography and consists of 14 repeats of the TraN – TraOCT – TraFCT trimer, homologs of VirB7, the C-terminal domain of VirB9 and the C-terminal domain of VirB10, respectively. This structure revealed that the inner lining of the channel is formed by the C-terminal domains of the 14 TraF subunits. The TraN-TraO subcomplexes surround the internal ring formed by TraF. The 33 residue long lipidated

TraN subunit is the outermost subunit of the complex whose external diameter is 172 Å. The unique structural features of VirB7XAC2622 allowed the authors to produce a model for the Xanthomonas T4SS outer membrane complex tetradecamer based on the structure previously solved for the pKM101 conjugation machine. In this model, Xanthomonas-specific VirB7XAC2622 oligomerization can occur while maintaining canonical VirB7-VirB9 interactions seen in the pKM101 complex. Figure 4B presents this putative model for the VirB7XAC2622VirB9XAC2620-VirB10XAC2619 outer membrane complex. Note that the VirB7 N0 domains (dark blue) adopt a variety of orientations with respect to the central ring and the membrane normal. This flexibility is derived from the conformational freedom of the VirB7XAC2622 regions immediately before and after residues 42-49 (magenta) involved in VirB7-VirB7 interactions. Though the sequence of the VirB7XAC2622 globular domain does not show sequence similarity to any

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SCIENCE HIGHLIGHTS

Figure 3: The VirB7XAC2622 N-terminus recognizes the VirB9XAC2620 C-terminal domain. (A) Superposition of the 15N-HSQC spectra of 15 N-VirB7XAC2622_24-139 alone (orange) and in the presence of 14N-VirB9XAC2620_154-255 (green). (B) Same as A, but with a close-up view of the central spectral region. The residues for which significant changes in peak positions were observed upon complex formation are indicated. (C) Weighted chemical shift changes (∆δcomp) of VirB7XAC2622 upon binding to VirB9XAC2620. (D) Residues affected by interaction with VirB9XAC2620_154-255 (residues 27-41; red) are color coded on the structure of VirB7XAC2622_24-139.

proteins of known structure, its topology resembles that of domains found in the following proteins: • the TonB-dependent receptors (periplasmic signaling domain), • the outer membrane secretin channel GspD from the type II secretion system (T2SS), • the secretin EscC from the Type III secretion system (T3SS), • the needle-like cell-puncturing device components gp27 and gp44 from long-tailed phages like T4 and Mu (9,10) and v) the Type VI secretion system (T6SS) protein VgrG. These domains are found

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at the N-termini of T2SS and T3SS secretins and have been denominated N0 domains which have also been identified in the Type IV pilus secretin PilQ and the filamentous phage secretin pIV. It is striking that in spite of its small and compact nature, domains with the VirB7XAC2622 topology are found only in a restricted number of proteins, all of which are involved in the transport of molecules across bacterial outer membranes. These observations suggest that all of these proteins may be distantly related and have evolved to adopt a variety of functions in the periplasm or outer membrane.


NMR and 1.0 Å X-Ray determinations of the structure of the VirB7 subunit of Xanthomoas citri.subsp.citri (citrus canker) and its interaction with virB9

Figure 4: VirB7XAC2622 structure and interactions in the context of the T4SS outer membrane complex.(A) Schematic organization of the VirB7XAC2622 protein. (B) Final molecular dynamics simulation of the putative model for the VirB7XAC2622-VirB9XAC2620-VirB10XAC2619 outer membrane complex. The VirB9 C-teminal domain is represented in red, the VirB10 C-terminal domain is shown in yellow and VirB7XAC2622 is in cyan (residues 22-41), magenta (residues 42-49) and dark blue (residues 50-139). One complete VirB7XAC2622 molecule is shown in green.

Acknowledgements

Dr. Ana C. Zeri and Dr. Maurício L. Sforça (Brazilian Biosciences National Laborator y, LNBio), Dr. Fabio C. Almeida and Dr. Ana P. Valente (Federal University of Rio de Janeiro),

Dr. Miriam Uemi (University of São Paulo) and the Brazilian Synchrotron Light Laboratory (LNLS) for providing access to their facilities for the realization of the NMR and X-ray crystallography experiments.

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2

The Crystal Complex of Phosphofructokinase-2 of Escherichia coli with Fructose-6-phospate

Ricardo Cabrera1, Maurício Baez1, Humberto M. Pereira2, Andrés Caniuguir1, Richard Garrat2 and Jorge Babul1

Departamento de Biologia, Facultad de Ciencias, Universidade do Chile, Chile Centro de Biologia Molecular Estrutural, Instituto de Física de São Carlos, University of São Paulo (USP), SP, Brazil. 1

2

Stereo view of the superposition of the Pfk-2·F6P (chain D) and Pfk-2·(ATP)2 structures.

Facility: MX2 Publication: Journal of Biological Chemistry, 2011, v.286, n.7, p 5774-5783 Funding: FONDECYT and FAPESP Corresponding author: Ricardo Cabrera: ricabrer@uchile.cl

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The Crystal Complex of Phosphofructokinase-2 of Escherichia coli with Fructose-6-phospate

Substrate inhibition by ATP (adenosine triphosphate) is a regulatory feature of the phosphofructokinases isoenzymes from Escherichia coli (P�k-1 and P�k-2). Under gluconeogenic conditions, the loss of this regulation in P�k-2 causes substrate cycling of fructose-6-phosphate (fructose-6-P) and futile consumption of ATP delaying growth. In the present work, we have broached the mechanism of ATP-induced inhibition of P�k-2 from both structural and kinetic perspectives. The comparison of the crystal structure of P�k-2 in complex having fructose-6-P with the previously reported inhibited form of the enzyme suggests a negative interplay between fructose-6-P binding and allosteric binding of MgATP. These effects occur simultaneously with the induction of a sigmoidal kinetic behavior (nH of approximately 2). In Escherichia coli, the glycolytic step of the ATP-dependent phosphorylation of fructose-6-P is catalyzed by two different phosphofructokinases, Pfk-1 and Pfk-2. Kinetic evidence indicates that these enzymes are subject to regulation by high concentrations of ATP . Pfk-2 belongs to the ribokinase family of sugar kinases. Within this group (the PfkB subfamily), inhibition of the enzymatic activity by MgATP has so far only been reported for Pfk-2. The kinetic mechanism of Pfk-2 has been characterized to consist of an ordered sequential addition of substrates where fructose-6-P binding to the active site is required for the catalytic binding of MgATP. However, it has been observed that, in the absence of fructose-6-P, MgATP is able to shift the state of aggregation of Pfk-2 from dimer to tetramer, leading to the proposal of an allosteric site for this nucleotide (2). Recently , our group reported the crystal structure of Pfk-2 in its tetrameric form bound to two ATP molecules and two Mg ions per monomer (the Pfk-2·(ATP)2 complex). One ATP corresponds to the phosphoryl donor substrate of the reaction and shows a singular interaction with a second ATP, which, we conclude, must be acting as the enzyme inhibitor. In the case of Pfk-2, inhibition occurs at low concentrations of fructose-6-P and high concentrations of MgATP . Although the increment of the fructose-6-P concentration decreases the inhibitory effect of MgATP, no kinetic mechanism has been proposed to model this phenomenon. The present work determined the crystal structure of Pfk-2 with fructose-6-P bound at the active site (the Pfk-2·F6P complex) to 2 Å resolution. It also allowed to compare this structure with the Pfk-2·(ATP)2 complex searching for insights into the conformational changes that originate substrate inhibition.

Crystallization and Data Collection

The enzyme was purified according to the method described by Parducci et al. The crystals were grown by the vapor diffusion method in a hanging drop consisting of 2 μl of the protein stock solution and 2 μl of a reservoir solution comprising 23% PEG 4000, 100 mm sodium acetate, pH 4.75, and 200 mm ammonium acetate. Crystals appeared after 3 days at 18 °C. X-ray diffraction data were collected at 100 K, on the MX2-LNLS beamline. The final structure revealed the presence of four monomers in the asymmetric unit associated in a way that strongly resembles the tetramer observed in the Pfk-2·(ATP)2 complex (Figure 1). The difference electron density map shows clearly the presence of a fructose-6-P molecule (Figure  2) in each subunit. Interactions with this ligand are established by residues coming from both domains and from the adjacent subunit via the β-clasp interface. Conformational changes at the active site of Pfk-2 were evaluated by structural superposition of the Pfk-2·F6P and Pfk-2·(ATP)2 complexes (Figure  3). Most of the residues involved in interactions with the ADP moiety of the substrate ATP molecule show a similar conformation in the two complexes. The main difference corresponds to a major displacement of helix α6 whose N terminus is involved in substrate ATP binding (Figure 3). The structure of the Pfk-2·F6P complex shows that most of the residues at the active site are prepared for the binding of the catalytic ATP, en route toward the ternary complex. On the other hand, as described above, it also demonstrates conformational changes that may indicate a potential negative interplay between allosteric ATP and fructose-6-P binding. For this reason, initial velocity experiments were performed to gain further insights about the pattern of inhibition that is originated by the interaction of these ligands with the enzyme.

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SCIENCE HIGHLIGHTS

Figura 1 - Overall structure of the P�k-2·F6P complex.

Panel a, the subunits A (dark gray) and D (light gray) are shown as ribbons, and the dimer BC is shown as a single surface. The fructose-6-P molecules are represented as space-filling models. Panel b, comparison of the tetrameric packing observed in the Pfk-2·(ATP)2 and Pfk-2·F6P complexes. A major loss in the surface area of the dimer-dimer interface is accounted for by the absence of contacts between the minor domain barrels in the fructose-6-P-bound form.

Figura 2 - The fructose-6-P-binding site of P�k-2. Stereo figure of the active site in chain D. A, electron density omit map (Fo − Fc) contoured at 3 σ for fructose-6-P is shown in red. Residues Lys-27 and Arg-29 come from subunit A and are highlighted in green. The locations of structural waters 7 and 12 are indicated by red crosses. B, a similar orientation of the active site highlighting the interactions described in the text. This figure was prepared using PyMOL.

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To understand how the allosteric binding of ATP affects the kinetic performance of Pfk-2, we here extend this characterization to cover the range of MgATP concentrations where inhibition is observed. As a starting point, we take the general scheme shown in Figure 4A, which includes the minimum number of intermediate species between the two structurally determined forms of Pfk-2. In this scheme, the catalytic ternary complex of Pfk-2 (with rate constant kcat1) could be formed from either Pfk-2·F6P or the intermediate specie Pfk-2-ATP, implicitly indicating a random mechanism. Additionally, this model allows the formation of a quaternary complex Pfk2·F6P-(ATP)2, generated by fructose-6-P binding to Pfk-2·(ATP)2 or ATP binding to the Pfk-2·F6P-ATP complex, that may be catalytically competent (kcat2). When MgATP was varied at several fixed concentrations of fructose-6-P (Figure  4B), a bellshaped dependence of the initial rate is observed. The increment of the fructose-6-P concentration attenuates the inhibitory portion of the curve and shifts the peak of maximum velocity toward higher concentrations of ATP. A negative interplay between fructose-6-P and MgATP in the forward side of the reaction was considered a better scheme to propose models. A global fit analysis of this data to models describing complete and partial substrate inhibition was performed. A better fit was obtained with a model of partial substrate inhibition under rapid equilibrium operating in the context of a random mechanism of substrate addition to the active site (Figure  4B). Statistical discrimination analyses between these models and a model that considers the Pfk-2·F6P(ATP)2 complex to be inactive also support the partial mechanism of substrate inhibition. A model of partial inhibition predicts that the structure of Pfk-2 is able to accommodate the allosteric ATP in a configuration, which is still compatible with catalysis by the enzyme, suggesting that in addition to the inactive Pfk-2·(ATP)2 complex, a partially active species, Pfk-2·F6P-ATP2, is formed. According to this result, fructose-6-P could bind the Pfk-2·(ATP)2 complex with a constant of 746 μm compared with 6 μm for the free enzyme. Initial velocities were analyzed as a function of fructose-6-P at several concentrations of MgATP (Figure 5). From these curves, secondary plots were obtained to follow the effect of MgATP on kcat, Km, and the Hill coefficient. A complex behavior was observed in which the effect of MgATP can be split into two regions of nucleotide concentration. On the


The Crystal Complex of Phosphofructokinase-2 of Escherichia coli with Fructose-6-phospate

Figura 3 - Conformational changes at the active site of P�k-2. Stereo view of the superposition of the Pfk-2·F6P (chain D) and Pfk-

2·(ATP)2 structures. The substrate ATP (ATPc), allosteric ATP (ATPa; adenine-Tyr-23 ϖ-stacking conformation), and F6P molecules are shown surrounded by several residues providing them with important interactions in their respective structures. Color is according to the Corey-Pauling-Koltun scheme except for carbon atoms in the Pfk-2·F6P complex, which are shown in green. Part of the secondary structural elements α6 and β3a (neighboring subunit) of the Pfk-2·F6P (lime) and Pfk-2·(ATP)2 (gray) complexes are shown.

one hand, up to 100 μm of MgATP, kcat for fructose6-P increases to reach a maximum value of 60 ± 4 s−1 (Figures 5A and 6A). This increment is consistent with the saturation of the catalytic site with MgATP because the apparent Km for MgATP was ~22 μm. Within the same interval, the saturation curves of fructose-6-P are hyperbolic (Figure 5A) with a half-saturation point (K0.5) that increases (from 4.5 to 30 μm) with the concentration of MgATP.

MgATP-induced Inhibition: Competitive or Partial?

Figura 4 - Inhibition of P�k-2 by MgATP. A, general kinetic model for MgATP-induced inhibition. E represents Pfk-2. The full model correspond to a partial mechanism of substrate inhibition that, in the absence of the formation of the Pfk-2·F6P(ATP)2 complex, stands for a pure competitive mechanism of substrate inhibition. B, initial velocities of Pfk-2 as a function of MgATP concentration at different fixed fructose-6-P micromolar concentrations (as indicated by the symbols). The continuous lines describe the expected variation of the initial velocity obtained by a global fit of the partial substrate inhibition model to the experimental data.

The comparison of the Pfk-2·F6P complex with the previously reported Pfk-2·(ATP)2 form shows conformational changes that indicate a mutual negative interplay between the binding of allosteric ATP and fructose-6-P. Two possible outcomes are expected: a quaternary complex Pfk-2·F6P-(ATP)2 could be formed or not. If the Pfk-2·(ATP)2 configuration were unable to bind the sugar phosphate substrate, a mechanism of pure competitive inhibition would be envisioned. However, this model poorly adjusts initial velocity curves for MgATP at different fixed concentrations of fructose-6-. Also, deviations are evident when analyzing the initial velocity curves for fructose-6-P at different fixed concentrations of MgATP, because either the sigmoidal behavior (Figures 5B and 6C) or

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Figura 5 - Kinetics for fructose-6-P at different concentrations of MgATP. Initial velocities of Pfk-2 were obtained with fructose6-P as variable substrate at different fixed concentrations of MgATP from 10 µm to 10 mm. Kinetics measured with 10 (●), 50 (○), 500 (), and 800 µm () of MgATP are shown in A. Kinetics measured with 1500 (●), 3000 (○), 5000 (), and 10000 µm () of MgATP are shown in B. The continuous lines represent the individual fit of each curve to the Hill equation.

the dependence of kcat with the MgATP concentration shown by Pfk-2 (Figure 6A) is not compatible with a pure competitive inhibition mechanism. In the case of Pfk-1, MgATP inhibition has been described as partial inhibition. If the Pfk-2·(ATP)2 complex structure were able to bind the sugar phosphate and perform catalysis, a mechanism of partial inhibition would be in operation. The decrease of kcat to reach a finite value is suggestive of the formation of a partially active Pfk-2·(ATP)2·F6P complex, but in opposition to Pfk-1, we do not detect a plateau for the variation of K05 for fructose-6-P even at 10 mm MgATP. In this case, the application of the linkage function analysis to Pfk-2 would result in a free energy of coupling with either an infinite value, when considering the competitive nature of K05 variation of fructose-6-P or a finite value when taking into account the variation of kcat for fructose-6-P because of its partial nature. Hence, a more complex mechanism is needed to apply such thermodynamic formalism to the substrate inhibition of Pfk-2. At any rate, we could fairly say that MgATP appears to be acting not only as a K-type inhibitor (antagonizing the binding of fructose-6-P) but also as a V-type inhibitor (decreasing the value of kcat). There are specific conformational changes that help to explain the decrease of the apparent affinity for fructose-6-P induced by MgATP. With respect to the

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interactions observed in the fructose-6-P complex, binding of the allosteric ATP seems to perturb the network of interactions with the phosphate moiety, mainly sequestering the side chain of Lys-27 and reorienting the side chain of Arg-90 out the active site (Figure 3). In the case of Lys-27, it forms interactions with both ATP γ-phosphates in the Pfk-2·(ATP)2 complex. Indeed, in two of the subunits, Lys-27 forms an additional water-mediated hydrogen bond to O3P of the phosphate group of fructose-6-P, reinforcing its central role in fructose-6-P binding. The kinetic characterization of Pfk-2 still requires further studies to fully describe the complexity of the inhibition mechanism. The use of allosteric site mutants and the structure determination of ternary complexes with nonhydrolyzable ATP analogues might be helpful in this elucidation.

Sigmoidicity of Fructose6-P Curves at Inhibitory Concentrations of MgATP

Although the homodimeric state of Pfk-2 is required for enzymatic activity and stability and is entirely consistent with the participation of both subunits in the formation of the active sites, no role for communication between these sites has been suggested previously.


The Crystal Complex of Phosphofructokinase-2 of Escherichia coli with Fructose-6-phospate

Different from Pfk-1, Pfk-2 presents an allosteric site in each subunit. Several contacts with either fructose-6-P or the allosteric ATP are formed by side chains from the β3a strand of the adjacent subunit of the dimer (Figure 3). It is therefore conceivable that binding of the allosteric ATP could also promote changes in the communication between the active sites via the residues directly involved in its binding, leading to cooperativity. It is noteworthy that some structural differences at the β-clasp interface are related to changes in the shape of the active site. For example, the large conformational change of Arg-90, necessary for fructose-6-P binding, leads to an alteration of the Trp-88 side chain conformation directly involved in intersubunit contacts . The loss of the π-cation interaction of Trp-88 and Arg-90 is consistent with a significant increment in the intrinsic fluorescence emission of the enzyme in solution, when comparing the fructose-6-P- and MgATPbound forms . In the Pfk-2·F6P complex, the surface area buried in the β-clasp interface is less than that in Pfk-2·(ATP)2 complex. In addition, whereas the Pfk2·F6P complex presents variable relative orientations of their minor domains, the Pfk-2·(ATP)2 complex is restricted to a fixed position. This is in agreement with previous observations from SAXS measurements of Pfk-2 in solution. In this way, conformational changes at the sugar phosphate site and at the relative orientation of the major and minor domains, inferred from the comparison of both crystal complexes of Pfk-2, are consistent with the behavior in solution and help to explain the negative interplay observed by enzyme kinetics. In addition to the β-clasp interface that originates the functional homodimer, the presence of MgATP generates the definitive dimer-dimer interface leading to homotetramer formation. Prior work from our group has shown that substrate inhibition induced by MgATP remains in mutant enzymes that are unable to form tetramers .

Figura 6. Effect of MgATP on the apparent kinetic parameters for fructose-6-P. A, kcat. B, K0.5. C, Hill coefficient. The values of each saturation curve were obtained from individually fitting the curve of Fig. 5 to the Hill equation and plotted against the concentration of MgATP.

Structural Determinants for Binding of Fructose-6-P in Different Scaffolds

Slight differences are observed between the structure of fructose-6-P in Pfk-1 and Pfk-2. For example, hydroxyls 3 and 4 appear to approach a more planar configuration with respect to the furanose ring. Dihedral O3-C3-C4-O4 of fructose-

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SCIENCE HIGHLIGHTS

6-P is −86.76 in Pfk-1 (Protein Data Bank code 1PFK chain A), compared with −33.23 observed in Pfk-2. The interaction of the Asp-14 carboxylate with both hydroxyls in Pfk-2 seems to be responsible for restraining this geometry, making it more equatorial than in Pfk-1, where these hydroxyls are bound by different residues. With respect to catalysis, Asp-127 in Pfk-1 is believed to be the general base, which abstracts a proton from OH1, thereby facilitating nucleophilic attack on the γ phosphate of ATP. In Pfk-2, the analogous base is also an aspartic acid (Asp-256), which is hydrogen-bonded to OH1 in the structure described here and presumably operates by a similar general mechanism. Prior to this report, from a total of 54 protein structures found in the Protein Data Bank containing a fructose-6-P ligand, only two correspond to phosphofructokinases (EC 2.7.1.11). Furthermore, within the PfkB subfamily, only Pfk-2 and the

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phosphotagatose kinases from Staphylococcus aureus (Protein Data Bank code 2jg1) and Listeria innocua (Protein Data Bank code 3jul) present threedimensional structures with the phosphoryl-acceptor substrate bound, showing there to be a relative paucity of structural information concerning the recognition and discrimination of sugar phosphates within this major branch of the ribokinase family. Together with the crystallographic studies of their respective complexes, a thorough sequence analysis of the PfkB subfamily is necessary to understand fully how sequence traits are related to selectivity toward their phosphosugar substrates. The atomic coordinates and structure factors (code 3N1C) have been deposited in the Protein Data Bank, Research Collaboratory for Structural Bioinformatics, Rutgers University, New Brunswick, NJ (http://www. rcsb.org/).


Macromolecular assembly of polycystin-2 intracytosolic C-terminal domain

Frederico M. Ferreira1,2, Leandro C. Oliveira3, Gregory G. Germino4, José N. Onuchic3, Luiz F. Onuchic1 Division of Nephrology, University of São Paulo School of Medicine, São Paulo, Brazil Laboratory of Immunology, Heart Institute, University of São Paulo School of Medicine, São Paulo, Brazil 3 Center for Theoretical Biological Physics, University of California at San Diego, La Jolla, CA 4 National Institute of Diabetes, Digestive and Kidney Diseases, Bethesda, MD 1 2

3 Diagram of the PC1 and PC2 and their interaction through coiled-coil domains in the C-terminal tails

Facility: SAXS Publication: PNAS 108, 9833, 2011 Funding: FAPESP, CNPq, LIM/USP, PKD, NIH and NSF Corresponding authors: Frederico M.Ferreira: ferreirafm@lim12.fm.usp.br José N. Onuchic: jonuchic@ucsd.edu Luiz F. Onuchic: lonuchic@usp.br

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SCIENCE HIGHLIGHTS

Autosomal dominant polycystic kidney disease (ADPKD) is the most common renal monogenic disease. It is genetically heterogeneous, being caused by mutations that can lead to the truncation or malfunctioning of PKD1 or PKD2 gene expression products. PKD2 encodes an mRNA of ~5, 3 Kb whose product is known as polycystin-2 (PC2). Most of PC2 seems to be localized in the endoplasmic reticule membrane. The authors presented the most comprehensive set of analyses yet performed, showing that PC2t forms a homotetrameric oligomer and proposed a new PC2 C-terminal domain delimitation and submitted it to a range of biochemical and biophysical evaluations, including chemical cross-linking, mass spectroscopy, dynamic light scattering (DLS), circular dichroism (CD) and small angle X-ray scattering (SAXS) analyses.

Autosomal dominant polycystic kidney disease (ADPKD) is the most common renal monogenic disease, with a prevalence of 1:400-1000 in Europeandescent populations. It represents a health problem of major medical, social and economic impact worldwide, accounting for ~5% of the patients with end-stage renal disease (ESRD) in the USA and ~8-10% in Europe. It has been estimated that approximately half million people suffer from polycystic kidney disease in the USA, the vast majority of them with ADPKD. This scenario makes this disorder the fourth main cause of ESRD. ADPKD is characterized by the development of multiple, bilateral renal cysts involving cortex and medulla, progressive enlargement of the kidneys, disruption of organ architecture and gradual loss of renal function. In fact, only half of the patients reach the age of 58 years without developing ESRD. Although renal manifestations predominate, ADPKD is a systemic disease that can lead to hepatics cysts, heart-valve abnormalities, intracranial aneurysms and other less frequent extra-renal manifestations. Its most significant renal manifestations and complications are represented by abdominal or flank pain, hematuria, urinary tract and cyst infections, nephrolithiasis and renal failure. Systemic hypertension and cardio and cerebral vascular complications, in turn, are also common key manifestations of this illness. Typically, the disease is clinically manifested in the third or fourth decade of life. The progression and age of ESRD, however, vary among affected individuals, even belonging to the same family. ADPKD is genetically heterogeneous, being caused by mutations that can lead to the truncation or malfunctioning of PKD1 (polycystic kidney disease 1) or PKD2 gene expression products. PKD1

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is located on chomosome 16p13.3, including 46 exons distributed over a genomic segment of approximately 53 Kb. This gene encodes an mRNA of ~14,2 Kb, translated in polycystin-1 (PC1), a membrane glycoprotein of 4303 aminoacids (aa) organized in a singular combination of multiple extracellular domains, 11 transmembrane domains and a small carboxyl-terminal portion turned to the cytoplasm. PC1 has been understood as a plasma membrane receptor, responsible for signal transduction from the extra to the intracellular environment, although it also behaves as an adhesion molecule. PKD2, in turn, maps to 4q22.1 and encodes an mRNA of ~5, 3 Kb whose product is known as polycystin-2 (PC2). PC2 consists in an integral membrane protein of 968 aa, is a member of the TRP (Transient Receptor Potential) channel superfamily, and functions as a Ca2+-permeable non-selective cation channel. While significant amounts of PC1 and possibly a small fraction of the PC2 molecules are in the plasma membrane, most of PC2 seems to be localized in the endoplasmic reticule membrane. Figure 1 shows a pictorial representation of the multidomain PC1 and PC2. Mutations in PKD1 are responsible for ~85% of the disease cases, while ~15% are owned to PKD2 mutations. Although the renal and extrarenal manifestations are common to ADPKD1 and ADPKD2, the disease tends to be more severe in patients bearing PKD1 mutations. This observation is based on an earlier course to ESRD and higher propension to develop systemic hypertension, urinary tract infection and hematuria in ADPKD1 patients, compared to ADPKD2. The renal cysts are covered by an epitelial cell monolayer with increased proliferation rate and


Macromolecular assembly of polycystin-2 intracytosolic C-terminal domain

Figure 1. Diagram of the PC1 and PC2 and their interaction through coiled-coil domains in the C-terminal tails. Details of the domains and regions of homology are shown in the key (from Torres VE, 2009).

less differentiation than normal tubular cells. Studies have showed that cysts are monoclonal in ADPKD, and indicated that cystogenesis follows a knudsonian mechanism. In such a context, although ADPKD is a dominant disease in regard to genetic transmission, at the molecular level the focal cyst formation mechanism is recessive, following a twohit mechanism. The first hit is represented by the germline mutation, which is present in all renal tubular cells of an affected individual, while the second hit is represented by a somatic mutation in the previously normal allele of a given cell. Experiments with genetically modified mice, with targeted mutations to Pkd1 or Pkd2, the PKD1 and PKD2 orthologous genes in those animals, also support this model. These findings are able, therefore, to explain the focal nature of ADPKD cystogenesis, as well as the intrafamilial and intra-organ phenotypic variability found in this illness. It must be pointed out, however, that recent reports have shown that broad and rapid renal cyst development require a third hit in mouse mature kidneys.

Several investigators have demonstrated the central role of PC1 and PC2 in the intracellular Ca2+ homeostasis of renal epithelial cells. Such studies strongly suggest that changes in this process are responsible for the abnormal hyperproliferative response of ADPKD cells to cAMP. In addition to its role in Ca2+ signalization, PC1 activation, in a PC2-dependent process, can activate JAK2, leading to phosphorylation and activation of STAT1, and generation of STAT1 homodimers, followed by p21 upregulation and decreased Cdk2 activity. Several studies indicate the involvement of the primary apical cilium in the pathogenesis of renal cystic diseases. It is currently admitted that the PC1PC2 complex present in the primary cilia of renal tubular cells acts as a sensor to physical or chemical stimuli, particularly to intratubular fluid flow, promoting Ca2+ influx through the PC2 channel. This influx, in turn, would lead to significant Ca2+ release from intracellular stores which would modulate subcellular activities such as cell proliferation, differentiation, apoptosis and gene expression. Since

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SCIENCE HIGHLIGHTS

the primary cilium can potentially modulate the centriole function, such signals might regulate the proliferation rate of developing renal epithelial cells, allowing them to progress to terminal differentiation and form mature tubules. The understanding of Ca2+ signaling is essential, therefore, to understand renal tubule morphogenesis and to elucidate the pathogenesis of polycystic kidney diseases. In this process, the PC1 and PC2 intracytosolic domains constitute key elements, given the interaction they have with each other and the interaction they have with other proteins. The lack of structural information about the PC2 intracytoplasmatic domain (PC2t), however, limits the understanding and broadening of biological mechanisms associated with ADPKD.

The macromolecular assembly of PC2t homoologomer

In spite of several reports, the macromolecular assembly of PC2t homooligomer continued to be an open question. Ferreira et al.(PNAS 108, 9833, 2012) have presented the most comprehensive set of analyses yet performed, showing that PC2t forms a homotetrameric oligomer. They have proposed a new PC2 C-terminal domain delimitation and submitted it to a range of biochemical and biophysical evaluations, including chemical cross-linking, mass spectroscopy, dynamic light scattering (DLS), circular dichroism (CD) and small angle X-ray scattering (SAXS) analyses. They have also used molecular dynamics simulations employing an all-atom structure-based model (SBM) to evaluate the macromolecular assembly of PC2t, by comparing the structures obtained from the simulation including the raw SAXS data and by reconstructing the distribution of states in solution using a system forced by entropy. The simulation results that the best-scored structures, in fact, are also the ones compatible with tetramerization. The PC2t particle envelope was assessed by SAXS data solution analyses. The data were collected at the D11A-SAXS beamline of the Brazilian Synchrotron Light Source (LNLS). Scattering data covering momentum transfers between 0.01 Å-1 < s < 0.3 Å-1 were recorded with a MAR145 image plate detector (Marresearch), using the 1.1488 Å wavelength, sample-detector distance of 1290.98mm and samples concentrations from 3 to 8 mg mL-1. Figure  2A displays the SAXS curves of PC2t in

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presence of 2.0 mM CaCl2 (PC2t-Ca) and 2.0 mM EGTA* (PC2t-EGTA). These results revealed PC2tCa and PC2t-EGTA apparent masses of 129 kDa and 139 kDa, respectively. Guinier analyses showed that the PC2t samples were diluted and monodispersed in both conditions, as demonstrated by the linearity of the curves at very low angles. The observation that both linear extrapolations are virtually parallel, in turn, indicates that the PC2t Guinier radii are very close: 52 ± 2 Å in the presence and 54 ±1 Å in the absence of calcium. In the reciprocal space, both curves superimpose very well in the low angle regimen. Such superimposition, however, is not observed for wider angles in the second and third sectors of the scattering curves (Figure 2A). Those differences are better appreciated in the real space by comparing their respective distance distribution functions between electron density pairs P(r), generated by the indirect Fourier transform of the scattering curves with the GNOM program. The PC2t P(r) functions in the presence and absence of calcium are shown in Figure 2B, revealing distance distributions slightly differ. In presence of calcium, PC2t presents a narrower P(r), centered in a smaller gyration radius (Rg) as a consequence of a smaller maximum dimension (Dmax). In contrast, the absence of calcium suppresses the typical P(r) multidomain shoulders and oscillations corresponding to intra and inter subunit distances, and Rg and Dmax swell toward a wider distribution of distances. The expansions of Rg and Dmax determined by calcium removal were from 55.9 ± 0.5 Å and 175 Å to 56.8 ± 0.6 Å and 188 Å, respectively. Calcium-induced differences in the PC2t scattering intensities were also detected by the Kratky plot (used to analyze the conformation of proteins and evaluate flexibility). The PC2t-Ca Kratky plot (Figure 2C) presents a narrow maximum at low-resolution range and a more dispersive profile for higher angles. Calcium removal, in turn, slightly shifted the low-resolution maximum to lower s, indicating that the Rg value is larger than the one obtained in the presence of calcium. In addition, some organization was gained for wider angles. These findings suggest a PC2t multidomain arrangement whose flexibility is modulated or altered upon calcium binding. The low-resolution particle shapes of PC2t-Ca and PC2t-EGTA homomultimers were restored from the scattering intensities using two ab initio procedures. *Metal chelate ethylene glycol tetracetic acid which has a high affinity for Ca ions.


Macromolecular assembly of polycystin-2 intracytosolic C-terminal domain

Figure 2. (A) PC2t small angle X-ray scattering intensities measured in the presence of 2.0 mM CaCl2 or 2.0 mM EGTA and their corresponding Guinier extrapolations (inside); (B) distance distribution functions between electron density pairs for PC2t in both conditions. (C) respective Kratky plots. (D) superimposition between the theoretical and experimental scattering curves from different reconstruction models. The curves were arbitrarily displaced on the vertical axis for clarity.

The particle envelopes were primarily calculated for low-resolution data (smax = 0.15 Ă&#x2026;-1) with the simulated annealing protocol implemented in the DAMMIN program. No symmetry was applied because higher order restraints neither improve the Ď&#x2021;2 fit between the theoretical and experimental scattering profiles nor stabilized the normalized standard discrepancies (NSD) among several independent reconstructions. Thirty independent simulations for the calcium and EGTA sets were filtered and averaged with the DAMAVER program. All of the ab initio models obtained from SAXS data yielded similar physical parameters. In the second ab initio method, the entire sets of the scattering data were employed in an attempt to identify the PC2t structural subdomains. The uniqueness of the shape restorations was also verified by comparing the NSDs of the superimposing solutions. Cluster analyses based on overall folding,

followed by selection of the closest model to the centroid of the largest clusters, were applied to identify a more representative ensemble of conformers. One hundred independent reconstructions were also performed for each calcium and EGTA dataset using the entire resolution range with the program GASBOR. The calcium restorations were clustered in four groups, whereas the EGTA set was clustered in nine groups (the isolated clusters were discarded). The superimposition of the theoretical and experimental scattering curves is shown in Figure 2D. The SAXS models from both reconstruction methods are presented in Figure 3. The I-TASSER C-Score function was employed to predict models based on alignments and convergence of structural assemblies. Despite their limitations, these models are sufficient to investigate the main features of the protein assembly. Three of

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SCIENCE HIGHLIGHTS

(A)

(C)

(B)

(D)

Figure 3: Final averaged PC2t SAXS envelopes. GASBOR reconstructions for: (A) PC2t-EGTA and (B) PC2t-Ca complete datasets;

and DAMMIM reconstructions for (C) PC2t-EGTA and (D) PC2t-Ca low-resolution data. (Models in blue are Ca and in red are EGTA; all models are presented in the same orientation).

the best-scored models were chosen to simulate the trimer, tetramer, and pentamer arrangements (Figure 4). Only the lowest score configuration is in satisfactory agreement with the SAXS data. Twelve simulations of each possible trimer, tetramer, and pentamer arrangement were performed. The best fit model for all simulations was achieved for a PC2t tetrameric arrangement in both calcium and EGTA conditions. Figure 4B shows the superimposition between the best fit model and the PC2t-Ca experimental data (χ = 11.4 and Rg = 51.8 Å), whereas Figure 4 C–E display the superimposition between the corresponding model and the PC2t-EGTA experimental data (χ =  7.5 and Rg = 53.8 Å). Simulations allowing increased degrees of deformation have not improved the χ values. An optimized combination of the best simulated models (SM) enhanced the agreement between the theoretical and experimental data for

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the EGTA condition. The combination of 70% of the SM1 model (χ = 7.5 and Rg = 53.8 Å), 20% of SM2 (χ = 8.4 and Rg = 53.5 Å), and 10% of SM3 (χ = 8.6, Rg = 54.0 Å) yielded a combined χ of 7.1. Combinations of the calcium-simulated models, on the other hand, have not improved the agreement between theoretical and experimental data in comparison to results obtained with individual models. In addition to a coiled-coil subdomain, the PC2 C-terminal intracytosolic domain includes an EF-hand subdomain and a flexible linker, structural features consistent with the experimental results. The various outlined sets of data, therefore, lead to a proposed model of tetrameric assembly for PC2t. The comparison of theoretical profiles and experimental SAXS data demonstrated that the trimeric or pentameric arrangements are inconsistent. Mixing multiple structures does not substantially improve the PC2t analysis, indicating further


Macromolecular assembly of polycystin-2 intracytosolic C-terminal domain

Figure 4. (A) Monomeric molecular model of PC2t predicted by I-TASSER. Five different predictions were made but only this configuration is in satisfactory agreement with the SAXS data. (B) Superimposition between the PC2t-Ca experimental data (blue) and the theoretical scattering curve from the simulated model SM1-Ca (black). (C), (D), and (E) Superimposition between the PC2t-EGTA experimental data (red) and the theoretical scattering curve, respectively, for the tetrameric simulated models SM1-EGTA, SM2-EGTA, and SM3-EGTA (black). SM1-EGTA shows a good fit in the very low angle region, SM2-EGTA shows a better fit in the middle angle region and SM3-EGTA shows a better fit in the higher angle region (all of them indicated by arrows). (F) Superimposition between the PC2t-EGTA scattering data and the theoretical scattering curve as a combination of the models presented in (C), (D), and (E).

assembly rigidity and therefore higher organization. This supports the notion that calcium increases the assembly stability. This region also provides information about the monomer extension and compactness of the assembly. The intermediate s region shows the presence of multiple conformations. By simply mixing three representative structures, a better theoretical adjustment to the experimental data is obtained. The large s region shows the existence of dynamical fluctuations varying from local ones all the way up to assembly compactness. The dynamic oligomerization hypothesis was also supported by

the SAXS data solution, using a recently developed approach. The applied molecular dynamics strategy was proposed for protein quaternary structure elucidation, particularly to such a flexible and complex system, and should be useful for other systems. The results of this study, in fact, are in accordance with all experimental analyses. The homotetrameric molecular model for PC2t should serve as a starting point to focus on questions directed to the PC2 channel architecture, gating mechanism and roles in ADPKD.

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Glutaminase C as key for the glutamine-based metabolism of cancer cells

Alexandre Cassago1, Amanda PS Ferreira1, Igor M Ferreira1, Camila Fornezari1, Emerson RM Gomes1, Kai Su Greene2, Humberto M Pereira3, Richard C Garratt3, Sandra MG Dias1 and Andre LB Ambrosio1 1

National Biosciences Laboratory (LNBio), Campinas, SP, Brazil 2 Veterinary Medical School, Cornell University, Ithaca, NY, USA 3 Instituto de Física de São Carlos, USP, São Carlos, SP, Brazil

Artistic representation (oilified) of the phosphatedependent Glutaminase C (GAC) crystal structure on top of tumor tissue slice stained for this protein

Facilities: MX2, SAXS, LPP, LEC, LBE and Robolab Publication: Proceedings of the National Academy of Sciences - PNAS 109, 1092 – 1097 Funding: FAPESP and LNBio Corresponding authors: Andre LB Ambrosio: andre.ambrosio@lnbio.org.br Sandra MG Dias: sandra.dias@lnbio.org.br

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Glutaminase C as key for the glutamine-based metabolism of cancer cells

In a recent paper published in PNAS 109, 1092 (2012)*Alexandre Cassago et al. present a collection of results, ranging from tissue and cell culture studies to x-ray crystallography and biochemistry, that collectively suggest that the lesser studied of the three so far identi�ied mammalian glutaminases, GAC, is the key glutaminase isozyme to supply for the increased tumor metabolic needs.

Though at very distinct rates, all cells in a living body grow and multiply. This process, called proliferation, must be tightly regulated in order for a healthy tissue â&#x20AC;&#x201C; an organ like the lungs for example â&#x20AC;&#x201C; to maintain its correct size and function. This if often accomplished through a carefully controlled event of production and release of proliferationpromoting signals, such as hormones, within a cell and its neighbors. In order for a eukaryotic cell like ours to reproduce, it must duplicate its macromolecular biomass (genome, proteins, cell membrane) before they go ahead and divide. The sugar glucose is one of the main nutrients that will fuel this progression. Through a series of multistep processes performed by proteins generally termed metabolism, glucose is broken down and/or condensed into new molecules that will result in the generation of both energy (in form of ATP) and the synthesis of building blocks (nucleic acids, other amino acids, lipids) for the assembly of the macromolecules mentioned above. Tumors are often a big ugly-looking deformed mass of cells that looks nothing like the organ it was removed from. Oncologists know, for quite some time now, that this is in great part due to the deregulation of the proliferation process. Cancer cells grow at their own will, at faster rates and at the expense of everything in its surroundings, like parasites. Therefore, cancer is generally defined as a group of diseases characterized by uncontrolled growth and spread of abnormal cells. In order to provide for this seemingly uncontrolled growth, the energetic and biosynthetic metabolism of cancer cells ought to be readjusted. Tumors must then capture great amounts of other extracellular nutrients, such as the amino acid glutamine, and quickly and efficiently metabolize them for shunting into the appropriate pathways. Glutamate production by mitochondrial glutaminase (GA), the first enzyme in glutaminolysis, is a key process for body homeostasis, and a crucial carbon donor for amino acid and lipid synthesis in

tumor cells. To date, three GAs have been identified in humans: the Liver-type (or simply LGA), the Kidneytype (or KGA) and Glutaminase C (GAC), a splice variant of KGA (both usually referred to as GLS1). In this extensive study, the authors present a collection of results, ranging from tissue and cell culture studies to x-ray crystallography and biochemistry, that collectively demonstrate that the lesser studied of the three so far identified mammalian glutaminases, Glutaminase C is the better adapted isozyme to supply for the increased tumor metabolic needs. They believe that a clear distinction of the molecular and structural specifics of the three isozymes, especially between the two isoforms encoded by the gene gls, Glutaminase C and Kidneytype Glutaminase, is mandatory in the context of both understanding the mitochondrial glutamine-based metabolism of cancer and the future development of target-specific therapeutics. In order to contribute to this distinction, they have introduced a number of original observations. They first show that although protein levels of the two kidney-type isoforms are increased in tumor tissues versus normal (Figure 1A), only Glutaminase C is compartmentalized in the mitochondria, where glutaminolysis takes place (Figure 1B). This is indeed surprising, as they both contain the canonical sequence that targets to the mitochondria. It is the first study in the literature where isoform-specific antibodies are used exploring their unique C-termini, which could explain these new findings. It has been known for several decades now that activity levels of the mammalian glutaminases respond to the presence of inorganic phosphate, though it is the first time that the three known isozymes are comprehensively studied together. The authors performed kinetic analysis of the three, and the outcome clearly shows that Glutaminase C most responsive to increasingly concentrations of the activator inorganic phosphate (Figure 2). This might be of particular importance in the context

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SCIENCE HIGHLIGHTS

Figure 1. KGA and GAC are enhanced in cancer, but only GAC is found in mitochondria. (A) box-and-whisker representation of the immunohystochemical analysis of human breast cancer tissue arrays.Isozyme specific antibodies show that protein levels of both GAC and KGA increase in tumor tissues when compared to their normal healthy counterparts, and correlate both with the degree of malignancy. (B) Fractioning of the breast SKBR3 and MDA-MB231, prostate PC3 and DU145 and lung A549 tumor cell lines followed by immunoblotting shows that KGA is found in the cytosol but not in the mitochondria, as opposed to GAC.

Figure 2. GAC has the highest activity in the presence of the activator inorganic phosphate. Kinetic analysis of the three isozymes shows that GAC becomes the most efficient isozyme already at phosphate concentrations around 10 mM. The differences are much enhanced as more phosphate is added to the reaction.

of glutaminolytic rates in tumors since hypoxic conditions may result in accumulation of this ion the mitochondria. Named after the discovery of its enzymatic activity by Hans Krebs, em 1935, mammalian glutaminases turned out to be more complex proteins, with a distinctive combination of additional motifs and functional domains. More specifically, the predicted presence of three ankyrin repeats (which exclusively function to mediate protein-protein interactions and have been found in proteins of diverse function such as cell-cycle regulators, transcriptional initiators, cytoskeletal proteins, ion transporters, and signal

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transducers) plus a nuclear receptor box motif (LxxLL, with x being any amino acid) found in coregulators of transcription via nuclear receptors, may explain this new observation. Hence, it would come as no surprise if the involvement of KGA in processes taking place outside the mitochondrial boundaries is soon demonstrated. Apart from the strong influence on the catalytic activity of GAC, no function can be predicted for its 53 amino acid long C terminus, based on the current knowledge on protein motifs and domains. In this context, GAC might be more relevant for the anaplerosis of the TCA cycle. Furthermore, by solving Glutaminase C crystal structure in three different states, i.e., ligand-free, and either bound to L-glutamate or inorganic phosphate (Figure 3A to 3D), in combination with structurebased biochemical studies, they offer the structural basis for protein tetramerization-induced lifting of a â&#x20AC;&#x153;gating loopâ&#x20AC;? as essential for the phosphate-dependent activation process. Amongst several new structural observations, they show that phosphate binds inside the catalytic pocket rather than the oligomerization interface, resulting in allosteric stabilization of tetramers and at the same time mediating substrate entry by competing with glutamate, therefore guaranteeing enzyme cycling (Figure 4). A higher tendency to oligomerize differentiates GAC from its splicing isoform and phosphate cycling in and out of the active site tells GAC specifically apart from the liver-type isozyme, known as inhibited by this ion. Besides, they believe the structural information will be particularly valuable in helping the future development of novel target-specific drug-based therapies to fight the aberrant cancer metabolism.


Glutaminase C as key for the glutamine-based metabolism of cancer cells

Figure 3. The crystal structure of GAC. (A) Orthogonal views of the tetramer in cartoon representation. Circles indicate, in chain A, the two

distinct domains comprising the full structure: amino-terminal and glutaminase. Though present in the crystallized construct, the C-terminus is heterogeneous in conformation and could not be successfully modeled. Top view of the cationic active site of GAC, represented by electrostatic surface mapping for the three crystal forms, show the presence of chloride (B), phosphate (C) and L-glutamate (D). 2Fo-Fc Fourier electron density maps of the ligands are contoured at 1Ď&#x192;.

Figure 4. Activation mechanism based on the gating loop and inorganic phosphate. Top view of the active site of GAC and its proximity to the gating loop (dashed line between Gly320 and Phe327). Phe327 is part of the buried interface upon tetramer formation. Fourier 2Fo-Fc electron density map (contoured at 1Ď&#x192;) shows that residues flanking the loop are well ordered. Relative positions of Pi, L-glutamate and the chloride ion can be seen inside the active site, as a result of structure superposition.

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5

Ferm Domain interaction with myosin negatively regulates FAK in cardiomyocyte hypertrophy Aline M Santos1,2, Deborah Schechtman3, Alisson C Cardoso1,2, Carolina F M Z Clemente2, Júlio C Silva2, Mariana Fioramonte1, Michelle B M Pereira1,2, Talita M Marin1,2, Paulo S L Oliveira2, Ana Carolina M Figueira2, Saulo H P Oliveira2, Íris L Torriani1,2, Fábio C Gozzo1, José Xavier Neto2 & Kleber G Franchini1,2 2

1 University or Campinas, Campinas, SP, Brazil National Laboratory for Biosciences (LNBio),CNPEM, Campinas, Brazil 3 University of São Paulo, São Paulo, Brazil

Representation of the myosin-binding cleft on the surface of the FERM FAK domain

Facilities SAXS, CXMS Publication Nature Chemical Biology. 8,102-110, 2012 Funding FAPESP and CNPq Corresponding author Kleber Franchini: kleber.franchini@lnbio.org.br

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Ferm Domain interaction with myosin negatively regulates FAK in cardiomyocyte hypertrophy

The amino-terminal region of FAK contains a region of proteins termed a FERM domain that are thought to mediate intermolecular interactions with sarcomeric myosin, inhibiting the interaction with a peptide activates FAK and promotes cardiac myocyte hypertrophic response. Several lines of evidence indicate that FAK functions to promote cardiac myocyte hypertrophy. However, a detailed understanding of how FAK is regulated in cardiomyocytes is still lacking. The authors perfomed extensive biochemical studies to demonstrate that sarcomeric myosin inhibits FAK through an interaction with FAK FERM domain and designed a decoy peptide corresponding to a short sequence of amino acids in the FAK FERM domain. These �inding reveal that FAK´s interaction with myosin has an important role in the regulation of FAK function that have an impact on the control of cardiomyocyte.

Focal adhesion kinase (FAK) is a tyrosine kinase that localizes to focal adhesions in adherent cells. Through phosphorylation of proteins assembled at the cytoplasmic tails of integrins, FAK promotes signaling events that modulate cellular growth, survival, and migration. The amino-terminal region of FAK contains a region of proteins termed a FERM domain. FERM domains are thought to mediate intermolecular interactions with partner proteins and phospholipids at the plasma membrane and intramolecular regulatory interactions. An intramolecular cleft of the FAK FERM domain mediates interaction with sarcomeric myosin. Chemical cross-linking, SAXS and mutational analyses confirm the interaction, and inhibiting the interaction with a peptide activates FAK and promotes cardiac myocyte hypertrophic response. Under prolonged stress, the heart can change its mass and diameter (i.e. remodeling) to cope with alterations in workload. This results from a variety of physiologic and pathologic conditions such as regular exercise training, hypertension and myocardial infarction. Because adult cardiac myocytes have little proliferative capacity, the structural remodeling of the heart primarily reflects the increase in size of individual myocytes (i.e. hypertrophy) in patterns that are unique to the inciting mechanical stress. In spite of its adaptive nature, in the context of pathological triggers myocyte hypertrophy sets in motion insidious processes that impair normal contractile function and shorten cell survival. These are seminal components in the development of heart failure, a condition in which hypertrophic growth is no longer able to compensate for increased workload. The fate of cardiac myocytes challenged by sustained mechanical stress has been shown to be

dependent on multifaceted cellular programs, which involve the action of diverse signaling molecules. A central challenge in this context is to define the precise regulation of molecular signals triggered by mechanical stress. Several lines of evidence indicate that Focal Adhesion Kinase (FAK) functions to promote cardiac myocyte hypertrophy1. Accumulated data on FAK show that it is a highly versatile scaffold and tyrosine kinase protein which can act in various subcellular contexts, particularly in modulating cellular functions related to cell adhesion such as migration, proliferation and survival. These broad range of functions place FAK at center stage in embryonic development, and pathological conditions, including cancer and cardiovascular disease. The 125-kDa FAK consists of an N-terminal band 4.1, ezrin, radixin, moesin (FERM) domain, followed by a tyrosine kinase domain and a C-terminal FA targeting (FAT) domain3. While none of these folded domains is unique to FAK, they are specifically modified in FAK resulting in a number of unique features. The FAK FERM domain is arranged in a globular clover-leaf structure formed by three independently folded subdomains F1, F2 and F3. The F2 subdomain interacts with the kinase C lobe, leading to an autoinhibited conformation that impedes access of ATP and substrates to the active site (Figure 1). Partnering with other proteins and lipids are thought to modulate the interaction between the FERM F2 subdomain with the kinase domain and thereby the inactive and active state of FAK5. FAK is promptly activated by mechanical stress and initiates intracellular signaling processes that coordinately regulate the hypertrophic response of cardiac myocytes6. However, the molecular

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SCIENCE HIGHLIGHTS

Figure 1. Overall structure of autoinhibited FAK including the FERM, linker, and kinase regions. In the autoinhibited state, the FERM domain (blue) binds to the kinase domain (red) through an interaction between the FERM F2 lobe and the kinase C-lobe. A section of the linker that contains the autophosphorylation site Tyr397 (orange) is located between the FERM F1 lobe and the kinase N-lobe (Lietha et al., 2007).

Figure 2. Structural basis for the FERM-myosin interaction determined by chemical cross-linking and computational docking. (a-b) Identification of the cross- linked peptides on the interface of the FERM-myosin complex. MS/MS spectrum of DSS (Disuccinimidyl suberate) cross-linked peptides (CLP-1 and CLP-2) from FERM- myosin complex is presented. (c) Molecular docking (obtained by GRAMM-X Protein- Protein Docking) of the complex FERM-myosin. The peptide proximity information provided by the MS/MS data was used to filter the docking best solutions (rms deviation of ~0.5Ă&#x2026; over all atoms).

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Ferm Domain interaction with myosin negatively regulates FAK in cardiomyocyte hypertrophy

mechanisms that regulate FAK activity in cardiac myocytes remain unclear. Previously, the authors reported evidence for a distinct pool of FAK, one that is linked to and may be negatively regulated by an interaction with the C-terminal tail of myosin heavy chain in the sarcomere, the contractile unit of cardiac myocytes7. In a paper that appeared in the January 2012 number of Nature Chemical Biology*, they performed extensive biochemical and structural studies to demonstrate that the FAK FERM domain interact with myosin through a wide cleft on its

surface. The studies were extended to show that the interaction with sarcomeric myosin inhibits FAK activity, which was demonstrated to be critical to maintain FAK inactive in cardiac myocytes while they are not being overstretched by mechanical stimuli. The structural basis for this interaction was initially determined by a combination of chemical crosslinking of the purified recombinant FERM domain and the myosin fragment coupled to identification of the hybrid peptides by mass spectrometry, and computational docking (Figure 2).

Figure 3. Validation of the molecular docking of the FERM-myosin complex based on SAXS data and mutational approaches. (a) Evaluation of docking results using the solution scattering profile from the complex FERM-myosin presenting the three docking models (GRAMM-X) most compatible with the SAXS experimental. (b) Surface representation of the FERM domain. The myosin binding site is presented in yellow and the mutated residues in dark blue. (c) Anti-6His and anti-myosin immunoblots from pull-down assay of HisFERM-WT, His-FERM-MUT-1, His- FERM-MUT-2, His-FERM-MUT-3, His-FERM-MUT-4 and His-FERM-MUT-5 performed with GST-MYO.

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SCIENCE HIGHLIGHTS

Figure 4. Representation of the myosin-binding cleft on the surface of the FERM FAK domain. (a) Surface representation of the FERM domain. The myosin binding cleft is presented in gray. (b) Ribbon representation of the FERM domain. The sub- structure of the FERM myosin-binding cleft is indicated in yellow. The most exposed amino acids at the interface (predicted by the SHARP2 server) are indicated and represented by sticks.

The computational models were validated by data obtained with small-angle X-ray scattering (SAXS) from solutions of the FERM-myosin complex and mutational approaches (Figure 3), obtained at the LNLS SAXS2 beamline. These data revealed a binding site for myosin on a wide cleft that sits beneath the three FERM subdomains of FAK (Figure 4). The role of this FERM-myosin cleft in the interaction of FAK with myosin was validated through two distinct, but complementary approaches. First, systematic mutations of the key aminoacid residues in the border of the FAK FERM cleft and myosin fragment. Second, we combined mutation data with structural modeling to design decoy peptides

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corresponding to FERM domain cleft. Consistent with structural and biochemical predictions, the decoy peptides competed with FAK for myosin binding. Further, functional studies demonstrated that the disruption of the FAK-myosin interaction resulted in activation of FAK and hypertrophy of cardiac myocytes. Such integrated biological approaches reveal an intriguing detail about the regulation of FAK, a mechanosensitive molecule, in cardiac myocytes. Knowledge thus gained is fundamental not only to understand the way molecules that control the myocyte response to mechanical stress but also to develop specific agents to interfere in the course of cardiac diseases.


Bactericidal silver nanoparticles: enhancing biological activity

Virginia Dal Lago1, Luciane França de Oliveira1, Kaliandra de Almeida Gonçalves2, Jörg Kobarg2 e Mateus Borba Cardoso1 Brazilian Synchrotron Light Laboratory (LNLS), Campinas, SP, Brazil National Biosciences Laboratory (LNBio), Campinas, SP, Brazil

1 2

6 Images of disk diffusion tests for small (A) and large (B) silver nanoparticles against Staphylococcus epidermidis

Facilities: SAXS2, LME Publication: Journal of Materials Chemistry 21, 12267 (2011) Funding: CNPq Corresponding author: Mateus Borba Cardoso – cardosomb@lnls.br

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SCIENCE HIGHLIGHTS

Silver has well-known medicinal properties. In the last decade, researches about them have reached the nanoscience level and the peculiar properties of nanoparticles promise new advancements. This work presents a methodological improvement that may make the tests with antibacterial silver nanoparticles faster – which is very welcome in an era when antibioticresistant bacteria grow dangerously. The novelty is that sets of nanoparticles with different sizes could be produced from the same reaction batch. That allows one to correlate more ef�iciently the structural properties of the nanoparticles with their antibacterial behavior. Tests were made for the in�luence of nanoparticle sizes on four bacterial strains. The smaller the nanoparticle is, the larger its antibacterial ef�iciency is. Besides, bacterial responses are dependent on nanoparticle sizes also in a very speci�ic way.

Medicinal properties of silver are known since the Antiquity. Burns and wounds have been treated with this metal for centuries; it has also been used to make water potable since the pre-Christian age. In this century, the studies about them reached the nanoscience age. Researchers have been exploring the surprising properties of silver nanoparticles (NPs) and investigating possible uses as diverse as in wound dressings, textile fabrics, wood flooring or catheters. But where does this bactericidal ability come from? This is what physicists should know in order to take advantage of it at its maximum. However, the answer is not completely clear yet. It is known that the size and shape of the nanoparticles have a fundamental role, but not exactly which is the mechanism of interaction between NPs and bacteria. This is what a team of researchers from the Brazilian Synchrotron Light Laboratory (LNLS) and from the National Biosciences Laboratory (LNBio), in Campinas, Brazil, is trying to help to unveil. Last year they produced an interesting contribution. If one looks carefully to what was done about bactericidal silver nanoparticle researches in the last years, one finds out that there is a gap in the scientific literature that could make improvements on the knowledge of their action. Indeed, although nanoparticles of many kinds, sizes and shapes have been tested, they were synthesized with different chemical reactions. That limits the possibilities of comparison of the different system performances and characteristics. In order to fill this gap, the group used a technique to test NPs with different sizes but produced from the same reaction batch.

NPs. To obtain the two sets from the same reaction batch, the authors had to synthesize a mix of NPs with several sizes and then proceed to a size-selective fractionation of the system through centrifugation (it makes heavier particles to go to the “bottom” and lighter ones to the “top”). The challenge was then to create a technique that could reach a successful fractionation. The main elements were the solvent used to disperse the nanoparticles (a surfactant – polyvinylpyrrolidone or PVP) and the strategy of tuning the amount of the surfactant to make the fractionation selective enough. In order to study the influence of size in the bacterial response, one should study it separatedly from other parameters such as shape. The technique used by the authors could also make this selection, since most of the obtained nanoparticles were spherical in both sets, large and small. That can be observed directly in images such as the ones depicted in Fig. 1, obtained by transmission electron microscopy (TEM) in the Microscopy Center (LME)

Small and large

The scientists chose to study nanoparticles with different sizes because scientific literature says that shape and size are the most important parameters to explain the different antibacterial abilities of different

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Figure 1. Transmission electron microscopy (TEM) images of small (A) and large (B) silver nanoparticles.


Bactericidal silver nanoparticles: enhancing biological activity

of the LNLS. Two sets of nanoparticles, with larger and smaller sizes, were obtained through centrifugation. The job was then to compare the performances of the two sets and to relate them to the structural properties of the nanoparticles. Actually, Fig. 1 shows that there were spherical, ellipsoidal and faceted nanoparticles in the solution; but a strong tendency to the spherical shape is evident. Anyway, eyes are not a very precise measurement instrument. A better assessment could be done with other techniques, such as the absorption spectra in the ultraviolet and visible region. The theory says that differently shaped nanoparticles absorb light at different wavelengths. So, if there were nanoparticles with several shapes in the solution, there should be several peaks in the spectrum. However, only one could be seen, indicating that there was no shape variation detectable with this technique. In order to see if the method is robust enough to provide data as precise as required, one should characterize the nanoparticles more quantitatively. In particular, it is needed to assess the degree of variation of the sizes in both sets of nanoparticles, small and large ones â&#x20AC;&#x201C; that is, their polydispersities. This is important, because the most homogeneous the set is, the most precise the obtained antibacterial data is. A technique sensible to these quantities is small-angle X-ray scattering (SAXS). Indeed, the accumulated know-how about the interpretation of SAXS results makes it a rich source of information. It may provide data simultaneously for several parameters, such as the radius, polydispersity and the surface smoothness of the nanoparticles. It turned out from SAXS experiments performed at the LNLS that the mean diameter for small NPs was 15.6 nm and for large ones was 20.8 nm. It was also found that polydispersity was larger for the smaller NPs (0.3) than for the larger ones (0.23).

bacteria were destroyed by the solution. The larger the inhibition zone is, the stronger the bactericidal effect of the nanoparticle is. This test was made with four different bacteria strains: Escherichia coli, Staphylococcus epidermidis, Micrococcus lysodeikticus and Staphylococcus aureus. The first result was that smaller nanoparticles were more effective than larger ones, as can be seen directly in Fig. 2 (the inhibition zones are larger for the smaller nanoparticles). In fact, smaller nanoparticles are more effective just because, as they are more numerous, the whole set of them in the solution has a larger surface area than the larger ones. This is a quite generic

Nanoparticle kills bacterium

Now, what does this nanoparticles-bacteria interaction say about how size affect bactericidal performance? The next step was to determine the antibacterial effect of each set of NPs and to correlate these two parameters. The ability of the nanoparticles to destroy bacteria can be assessed with the wellknown disk diffusion test. Small amounts of the solution with the silver nanoparticles were dropped over small paper disks that were put inside a bacterial colony, as in Fig. 2. The dark rings around the paper disks, called inhibition zones, are regions where

Figure 2. Images of disk diffusion tests for small (A) and large (B) silver nanoparticles against Staphylococcus epidermidis. Numbers represent the load silver mass (in Âľg) in each paper disk.

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SCIENCE HIGHLIGHTS

behavior. However, in the scientific literature there are evidences that bacteria – and viruses – respond to nanoparticle sizes in a very specific way. This effect could also be detected with the disk diffusion test by means of a more accurate analysis of the data, as in Fig. 3, where different bacteria strains produced different inhibition zone sizes. Thus, the authors could produce differently sized nanoparticles from the same v batch, isolate one specific relevant parameter for study – their sizes – and produce results consistent with the known data in the literature. This method may speed up bacterial and/or

viral affinity tests and increase the efficiency of the current research techniques. In fact, the emergence and persistence of antibiotic-resistant bacteria in several regions of the world make these studies urgent; methods to make them faster are welcome. The original work was published in the Journal of Materials Chemistry 21, 12267 (2011) by Dal Lago, V.; Oliveira, L. F.; Gonçalves, K. A.; Kobarg, J. And Cardoso, M. This paper was also featured on the journal cover. All figures were taken from the original article above.

Figure 3. Diagrams with the disk inhibition zone sizes (from disk diffusion tests) for Escherichia coli (A), Staphylococcus epidermidis (B), Micrococcus lysodeikticus (C) and Staphylococcus aureus (D). Small nanoparticles: light-gray bars; large nanoparticles: dark-grey bars. ND stands for “Not determined”, since no inhibition was observed in these cases.

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Palladium cools nickel phosphide synthesis

V. Teixeira da Silva1, L. A. Sousa1, R. M. Amorim2, L. Andrini3, S. J. A. Figueroa4,5, F. G. Requejo3, Flavio C. Vicentin6 NUCAT/PEQ/COPPE/Federal University of Rio de Janeiro (UFRJ), Rio de Janeiro, RJ, Brazil Seção de Química, Instituto Militar de Engenharia, Rio de Janeiro, RJ, Brazil 3 INIFTA and Dto. De Física, Fac. De Ciências Exactas, Universidad Nacional de La Plata, CONICET, La Plata, Argentina 4 CINDECA, Dto. Química, Fac. De Ciências Exactas, Universidad Nacional de La Plata, CONICET, La Plata, Argentina 5 European Synchrotron Radiation Facility (ESRF), Grenoble, France 6 Synchrotron Light Brazilian Laboratory (LNLS), Campinas, SP, Brazil 1 2

7 Proposed model to explain how palladium works to decrease reduction temperature to produce nickel phosphate supported on silica

∆ H2

Facilities: SXS, DXAS Publication: Journal of Catalysis 279, 88 (2011) Funding: CNPq, CAPES, CONICET, ANPCYT Corresponding author: Victor Teixeira da Silva – victor.teixeira@peq.coppe.ufrj.br

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SCIENCE HIGHLIGHTS

Nickel phosphide has a strong potential to improve the hydrotreating of several oil fractions because it is much more active than the commercial catalysts currently employed in re�ineries all over the world. However, the temperature necessary to synthesize this compound, above 700 degrees Celsius, precludes commercial viability in industry. Besides, there are still some gaps in the knowledge about its synthesis mechanisms, the solutions of which could make further scienti�ic improvements easier. One of these gaps is which is the exact nature of the intermediate nickel phosphide precursor that appears at the end of the �irst stage of the production process. A team of scientists from Brazil, Argentina and France could develop a method to produce nickel phosphide at a temperature 220 degrees lower than the usual without the drawbacks present in other ones proposed in the literature. The key strategy is to add small amounts of palladium to the precursor. Besides, they could also identify that the unknown precursor is nickel phosphate and also to propose a model to explain why palladium produces such effects.

Catalysis is a crucial element in the industrial transformation of petroleum into its derivatives. Improvements on the catalyst performances may potentially decrease prices for several products in the market and there is continuous research for this aim in the world. In the late 1990’s, scientists discovered a catalyst that is better than the commercially used ones for some key reactions such as hydrodesulfurization (HDS) and hydrodenitrogenation (HDN): nickel phosphide (Ni2P). However, the necessary temperature for its production, above 700 degrees, is too high to allow its use in industry. So now the challenge is how to make this temperature lower. There are some suggestions in the scientific literature, but until now each one of them had some drawback that precluded commercial use. Usually, the investigated methods result in undesirable side products like HCl and NaCl (that are responsible for corrosion) or Ni12P5, that decrease the performance of the catalyst; in other cases the problematic chemicals are among the precursors – it is the case of phosphine, that has security restrictions. The issue may have been solved by a team of researchers from three countries and five institutions: the Federal University of Rio de Janeiro (UFRJ), the Engineering Military Institute (IME), also in Rio, the Synchrotron Light Brazilian Laboratory (LNLS), in Campinas (Brazil), the National University of La Plata, in Argentina, and the European Synchrotron Radiation Facility (ESRF), in Grenoble, France. The group, lead by Victor Teixeira da Silva from UFRJ, just discovered that, if a small amount of palladium was added at a certain intermediate stage of the Ni2P synthesis process, the necessary temperature for its

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production decreased by about 200 degrees. Besides, the precursor of nickel phosphide present in this intermediate stage had still not been completely identified in the literature, but the researchers managed also to fill this gap. Finally, they pictured a model to explain partially the mechanism through which the whole synthesis process happens and how palladium acts.

What is the precursor?

Nickel phosphide is usually synthesized either in bulk form or over a support of silica (SiO2); the researchers used the latter. The result was a mixture of mainly silica and Ni2P phases, with palladium phases arranged in some way among them (in which way is something that the group could also propose). The production of Ni2P has two stages. The first one produces an intermediate substance, called the precursor, and the second one transforms the precursor into nickel phosphide. The problem is that, although scientists know how to produce Ni2P, they were not sure about the nature of the precursor. It was called simply as NixPyOz, because one knew that there were nickel, phosphorus and oxygen atoms in it, but not in what amount neither in which assemblage. There are some hypotheses in the literature, but none of them is secure enough. However, the authors discovered strong evidences that the precursor is Ni3(PO4)2, or nickel phosphate, based mainly on X-ray diffraction. This is the second major achievement of their work, the first being the synthesis temperature decrease. More precise measurements with P L2,3 X-ray absorption near-edge structure (P L2,3 XANES)


Palladium cools nickel phosphide synthesis

are currently being conducted in the laboratory to verify and consolidate this conclusion.

What the noble metal can do for us?

In the second stage of the production of nickel phosphide, the precursor Ni3(PO4)2 was transformed in Ni2P by means of a reduction step called temperatureprogrammed reduction (TPR). It is this last technique that demands a so high temperature to work, because chemical reduction, responsible to take off the oxygen atoms from Ni3(PO4)2 so as to form Ni2P, simply does not happen at temperatures lower than 700 degrees. It was between these two stages that palladium had to be added for having the reduction to occur at a lower temperature. To show that palladium could cause such effect, temperature and reduction rates should be monitored during the whole second stage process in order to identify at what value reduction started. In TPR, temperature is raised slowly (such as 1 to 10 degrees per minute). Reduction rate was monitored by means of a mass spectrometer coupled to the TPR facility. It allowed one to determine quantitatively what species passed through a leak valve while the reaction ran – in

particular the amount of water, because it indicates the rate of reduction of the phosphate species. Figure 1 shows the water formation profile for four situations: with no palladium (curve d) and with 0.1, 0.5 or 1% (in weight) of palladium (curves e, f and g, respectively). When there is a peak, oxygen is being thrown away from the phosphate. So this is a sign that reduction started to happen. The picture shows that, without palladium, reduction rate assessed this way reaches its maximum at 993 K. With 1% of palladium (curve d), it occurred at 772 K, or 499 Celsius degrees – a reduction of about 220 degrees! Palladium did more than that. It also decreased the time necessary to complete the reduction. This is reflected in the sharpness of the peaks of Figure 1 (compare the peak in curve d in Figure 1 with the others), but it could be assessed more precisely through measurements performed at LNLS, with Ni-K XANES. Well, all of that seemed to work very nicely; however, the result of the whole process was not exactly nickel phosphide, but nickel phosphide with minuscule palladium particles spread through it. Now, does this mixture share the same virtues as Ni2P that make it so potentially suitable to petroleum derivatives industry?

Figure 1. Water formation profile during TPR for NixPyOz/SiO2 (d), 0.1% Pd NixPyOz/SiO2 (e), 0.5% Pd NixPyOz/SiO2 (f) and 1% Pd NixPyOz/ SiO2 (g). The temperature was raised at a rate of 10 K/min.

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The answer seems very likely to be: yes! In order to verify that, the scientists submitted their new product to a typical reaction used in this kind of industry, hydrodesulfurization (HDS), and compared the results obtained with both Ni2P alone and Ni2P with palladium added. The conclusion from this catalytic testing was that the selectivity of nickel phosphide – the amounts of each resulting products from the reaction – was kept almost unchanged with the noble metal. This is an indicator that the chemical behavior of nickel phosphide with palladium is similar to the version without it and possible indicates that during the reduction the palladium particles either migrate to the interior of Ni2P or are recovered by it therefore not participating in the reaction at all.

Why does it work?

The team built a model to explain the mechanisms involved. The key phenomenon seemed to be hydrogen spillover. Indeed, hydrogen has a central role in the mechanism. In the reduction reaction, hydrogen atoms are firstly adsorbed at the surface of the reactant and then react with it. If they can’t be adsorbed – because of a too high potential barrier –, then reaction cannot occur. The high temperature is needed just to provide the necessary energy to overcome this potential barrier. Well, it happens that palladium has a lower potential barrier than nickel. Besides, when hydrogen is adsorbed on the palladium nanoparticles the H – H bond is broken generating atomic hydrogen that is much more reactive then molecular hydrogen and is mobile in the solid surface. This last phenomenon is the so-called hydrogen spillover. So, in these conditions a lower temperature is needed to make hydrogen overcome the potential barrier and react with nickel. This seems to be how palladium works. This mechanism also provides explanation for some of its other effects. Indeed, it explains beautifully an intriguing feature in Figure 1: in some cases two peaks appear (such as in curve e). Well, that Figure indirectly shows the amount of oxygen left from the reaction site and so its curves are indicating at what temperature the reduction begins. This means that it is already known that one of the peaks is due to the reduction. What does the other mean? The proposed explanation is the following: if palladium acts through hydrogen spillover, then nickel phosphide will be formed near palladium particles. So it is reasonable to assume that eventually palladium action will stop because it will be partial

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or totally covered by Ni 2P (because the latter formed over palladium and/or because palladium migrated to the interior of the Ni2P-Ni3(PO4)2/SiO2 complexes – see Figure  2). When this happens, Ni3(PO4)2 will be able to be reduced again only when the temperature reaches the value necessary to do it without palladium. So reduction stops when the available palladium is finished, but it starts again when the temperature becomes high enough to start it without the help of the noble metal. At this moment, the second peak is produced.

The palladium effect

The last goal was to investigate how the resulting system works for what it was designed – for example, the HDS reactions. Several amounts of palladium were tested – 0.1%, 0.5% and 1% to assess its influence over HDS performance. This is described in Figure 3. The Figure  shows that the catalytic activity of the system follows the trend: 0.1% Pd > 1% Pd ≈ 0.5% Pd > 0% Pd (where by “0% Pd” we mean just Ni2P/ SiO2 without palladium). Now, there is an interesting (although partial) correspondence with the degree of reduction, shown in Figure 4. The degree of reduction was obtained by means of P-K XANES measurements at the K edge of phosphorous, performed at LNLS. This is an interesting phenomenon that demands an explanation. First, note that the catalytic test was made after a partial reduction of the Ni3(PO4)2 sample (in order to chemically activate it), so there existed some, say, Ni2PyO1-y among the final Ni2P phases. The key hypothesis to explain the observed trends is that a fundamental process in the HDS reaction is the substitution of the remaining oxygen atoms by sulfur ones: Ni2PyO1-y → Ni2PyS1-y Then the proposed reasoning is: a larger reduction degree means fewer oxygen atoms in the sample; fewer oxygen atoms mean fewer oxygen available to be substituted by sulfur atoms; and this means lower HDS performance. So a larger reduction degree leads to a lower HDS performance. This is the correlation that explains the parallelism between Figure 3 and 4. But the sample with no palladium (0% Pd) seems do break this parallelism. The cause is related to the partial reduction to which the samples were previously submitted as a preparation for the catalytic test. In this phase, harsher reduction conditions were used in the sample with no palladium, what resulted in a more reduced system than it is shown in Figure 3.


Palladium cools nickel phosphide synthesis

Figure 2. Proposed model to explain how palladium works to decrease reduction temperature to produce nickel phosphate supported on silica. As the Figure shows, nickel phosphate is formed near palladium atoms; the higher the palladium content, the higher the phosphate reduction into Ni2P.

All of this indicates a method to produce nickel phosphide at a temperature 220 degrees lower than the usual methods, without the drawbacks presented by the proposed alternatives in the literature. The knowledge of the nature of the precursor, nickel phosphate, and the proposed model for the action of palladium are important to further development in the subject and contribute to make Ni2P suitable for industrial use.

Currently, a collaborative work between UFRJ and LNLS teams is studying if other noble metals such as Pt and Rh have the same effect as Pd (and yes, they do!) and pinpointing the exact localization of the noble metal nanoparticles after the reduction step. The original work was published in the Journal of Catalysis 279, 88 (2011) by Silva, V. T., Sousa, L. A., Amorim, R. M., Andrini, L., Figueroa, S. J. A., Requejo, F. G. and Vicentin, F. C. All figures were taken from the original article above.

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SCIENCE HIGHLIGHTS

Figure 3. Catalytic activity of 30% Ni2P/SiO2 (a), 1% Pd/SiO2 (b), 0.5% Pd 30% 30% Ni2P/SiO2 (c), 1% Pd 30% Ni2P/SiO2 (d) and 0.1% Pd 30% Ni2P/SiO2 (e).

Figure 4. Degree of reduction of samples NixPyOz/SiO2, 0.1% Pd NixPyOz/SiO2, 0.5% Pd NixPyOz/SiO2 and 1% Pd NixPyOz/SiO2), estimated from P-K XANES data and relative to a bulk Ni2P sample.

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8

How the new iron-based superconductors work

E. M. Bittar1, C. Adriano2, T. M. Garitezi2, P. F. S. Rosa2, L. Mendonça-Ferreira3, F. Garcia1, G. de M. Azevedo4, P. G. Pagliuso2,5 and E. Granado2,1

Brazilian Synchrotron Light Laboratory (LNLS), Campinas, SP, Brazil Instituto de Física “Gleb Wataghin”, UNICAMP, SP, Brazil 3 Instituto de Física e Matemática, Federal University of Pelotas (UFPel), RS, Brazil 4 Instituto de Física, Federal University of Rio Grande do Sul (UFRGS), RS, Brazil 5 Department of Physics and Astronomy, University of Califórnia Irvine, USA 1 2

Derivative of the XANES spectra

Facility: XAFS2 Publication: Physical Review Letters 107, 267402 (2011) Funding: FAPESP, CNPq Corresponding author: Eduardo Bittar – eduardo.bittar@lnls.br

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SCIENCE HIGHLIGHTS

Iron-based superconductors are the new stars in the world of solid state physics. Discovered in 2008, they rescued the frustrated enthusiasm stroken by their older cousins, the �irst hightemperature (high-Tc) superconductors, 26 years ago. Indeed, although the latter were the �irst to work above the long-battled 77 K limit that allowed commercial viability, they suffered from unpredicted technical drawbacks and failed to reach the market. It is true, however, that until now the new iron-based materials are superconductors only up to 55 K. In order to to overcome the 77 K threshold, the knowledge about how superconductivity arises in them is crucial. Unhappily, this mechanism is not known yet. Besides, theoretical calculations have indicated that a widely accepted hypothesis about it – based in electron doping – could be wrong. Last year, scientists in the LNLS experimentally showed that what was thought as the key ingredient to these superconductors, the iron atom, is not affected by electronic doping and indicated a substitute hypothesis.

Superconductivity discovery is already more than one hundred years old but Mankind still waits for the technological revolution it promised. The reason is that the temperature needed for materials to become superconductors (the “critical temperature”, Tc) is so low that it has to be maintained with liquid helium, which too high cost precludes most commercial applications. Even the high-Tc ceramic cuprate superconductors, that raised big enthusiasm since their discovery in 1986, failed to be useful for most practical applications. Although they work above the nitrogen liquefaction point (77 K) that theoretically warrants market viability, technical drawbacks such as their brittleness remain unsolved and have kept these new materials far from the market. In the last decades, however, some new promising possibilities have been explored. The last good news came in 2008, when scientists discovered that some intermetallic iron-based crystals became superconductors at up to 55 K, excitingly near the liquid nitrogen liquefaction temperature. They have some similarities with the ceramic cuprates – e. g., both become superconductors when they are doped with small amounts of certain elements (see Figure 1) and both crystals are layer-structured, with copper oxide (or iron plus arsenic) layers sandwiched between other elements, with superconductivity occurring only bidimensionally along each layer. The most interesting features are the differences, however. First, the undoped version is an antiferromagnetic material and in general magnetism is not compatible with superconductivity. This is very surprising. Besides, the mechanism through which they become superconductors is still unknown.

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Figure 1. Phase diagrams for BaFe2-xCoxAs2. The variable x is the

amount of cobalt in the material. There is a range of value of x for which superconductivity arises, indicated by the blue shadowed area. There are three phase diagrams superposed, each for one of the three measured quantities: for electrical resistivity (ρ), for specific heat (Cp) and for magnetic susceptibility (χ). The colored dots indicate the measured critical temperature for several x and for: superconductivity (Tc), crystalline structure (TE) and antiferromagnetism (TN) transitions. The shadowed areas are just a guides to the eye.

All of this opens room to new routes of research to eventually surpass the 77 K threshold. The most studied of the new materials is BaFe 2As with a small part of the Fe atoms substituted by cobalt – represented by BaFe2-xCoxAs2.

The true meaning of “electron doping” in the new superconductors

The knowledge about the superconductivity mechanism is important because it is a crucial hint to search for better, higher-Tc superconductor materials. To reach this knowledge, models are made with the


How the new iron-based superconductors work

help of well-based initial hypotheses and then tested in the laboratory. Since their very discovery, a widely accepted hypothesis was that the BaFe2-xCoxAs 2 superconductivity arise because of changes in the electronic structure of their iron atoms, caused by the presence of the dopant – or, more specifically, because of “electron doping”. Well, if scientists were using this assumption to guess models for the detailed mechanism, then a work published last year by a group of researchers from Brazil is very welcome, because they discovered that the assumption is probably not correct. In fact, the team, lead by Eduardo Bittar from the Brazilian Synchrotron Light Laboratory (LNLS), confirmed experimentally at the LNLS what was already suspected because of theoretical calculations made in 2010. In reality, the old assumption appeared to be consistently based on reliable experimental data and theoretical reasoning. It was already known that the high-Tc cuprates discovered in 1986 could have their superconductivity explained by charge carrier (electrons or holes) doping, via chemical substitution (e. g., the substitution of some irons by cobalt as above). It was natural to assume that the mechanism in the case of BaFe2-xCoxAs2 could be similar. Accordingly, as early as 2008 – the year of discovery of the new material – calculations with density functional theory (DFT) indirectly indicated that the exceeding valence electrons that cobalt bring to the crystal were responsible for alterations in the charge density distribution around the iron atoms in the crystal – that is, electron doping. In 2011, experiments with angular resolved photoemission spectroscopy (ARPES) also pointed indirectly to the same conclusion. Electron doping seemed to be a solid hypothesis. But meanwhile other findings blurred this beautiful scenario. In 2009 and 2010 superconductivity was observed in some undoped iron-based compounds. So it seemed that doping was not always necessary for superconductivity to appear in such crystals. Besides, in 2010 new calculations were done with DFT associated with a supercell approach. Contrary to the previous results, they showed that the presence of cobalt has little effect on the charge density distribution of the rest of the material! How to explain these different conclusions? In reality, the old hypothesis was not as solid as it might seem. The 2008 calculations were made using DFT with virtual crystal approximation. However, either this approximation or the ARPES experimental technique can measure the charge density distribution

only indirectly. More exactly, what the virtual crystal approximation allowed researchers to assess was the shift in the chemical potential due to increasing cobalt content; as the result was consistent with the electron doping phenomenon it led scientists to assume that superconductivity had something to do with the changes of the iron charge distribution. This assumption was reflected in the terminology widely used to refer to the new material, “electron-doped BaFe2As”.

X-ray spectroscopy dissipates the doubts

The last word should be brought by experiments that could measure the charge density around atoms of specific elements more directly. That is, one needed some technique that could identify how the presence of cobalt changes the electronic energy levels of the iron atoms. This can be done with X-ray absorption near edge structure (XANES) spectroscopy – what was exactly what Bittar’s team did at the LNLS. The XANES spectra (at the iron K edge) for BaFe2-xCoxAs2, for several cobalt contents, from zero (that is, no cobalt) to 19% (x = 0.38) are shown in Figure 2. These absorption spectra are related to the electronic transition from the Fe 1s core level to Fe 4p unoccupied states. If the local electronic occupation is changed, it is expected a shift of the threshold absorption energy. In the first derivative of the absorption curve, is easier to observe that the edge remains unchanged while the cobalt content is varied. So the energy level position does not change with the presence of cobalt. To make this point clearer, it is interesting to see how things would be if there were indeed an effective electron doping in BaFe2As iron atoms, and to compare such case with the no-electronic doping situation above. This can be done if one studies BaFe2As doped with lanthanum – that is, Ba1-xLaxFe2As2 –, because it is assumed that substitution of barium (Ba) with lanthanum does cause electron doping in Fe. In Figure 3, doping was simulated with theoretical calculations for several lanthanum contents. One can see in the figure that, in this case, the position of the peaks varies substantially with x (see the continuous curves). That means that the electronic structure of the iron atoms in BaFe2-xCoxAs2 – and so the charge density distribution around it – is not affected by cobalt content. Certainly it indicates its superconductivity might not be only due to electron doping because that

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SCIENCE HIGHLIGHTS

CoxAs2 at room temperature. Prominent peaks and shoulders are indicated as A-F. (b) First derivative of the XANES spectra in (a). Note the correspondence of the structures A-F in (a) and (b).

Figure 3. The filled symbols represent Fe K edge XANES spectra first derivative A’, B’, C’, D’ and E’ feature (see Figure 2) positions as a function of Co substitution (x) in BaFe2-xCoxAs2. The solid lines and open symbols are the expected red shifts caused by electron doping, obtained by simulated XANES spectra of Ba1-xLaxFe2As2 (x = 0.00, 0.25 and 0.50) model compounds. The dashed lines indicate the feature positions for x = 0.

should directly cause variations in the iron charge distribution. The old electron-doping hypothesis may have broken down But, if electron doping is possibly not solely responsible for superconductivity in BaFe2-xCoxAs2, another question is immediately raised: what makes this material to superconduct? Even though cobalt doping does not cause sensible changings in the iron charge density distribution, it obviously does cause other structural changes in BaFe2As. Superconductivity rising seems to be related to other two phase transitions caused by cobalt doping: a transition from tetragonal to orthorhombic crystalline structure and a destabilization of the spin density wave ground state of the sea of electrons.

Additionally, the presence of cobalt atoms causes a perturbation in the crystalline structure by itself, changing slightly the distance between the atoms in their vicinity. The authors concluded their paper with a theoretical reasoning about the energy balance between these different phenomena. Their conclusion is that the modification in the bonding energy between iron and its neighbor atoms might have a crucial role in the appearance of superconductivity in BaFe2As doped with cobalt. Whatever the explanation for the superconductivity of B aFe 2 As may b e, t hes e lo c a l energet ic perturbations should be taken as a fundamental element of it.

Figure 2. (a) Normalized Fe K edge XANES spectra of BaFe2x

54 | ACTIVITY REPORT 2011


DNA nucleobases may survive in outer space for billion of years S. Pilling1 , D. P. P. Andrade1, E. M. do Nascimento2, R. R. T. Marinho2, H. M. Boechat-Roberty3, L. H. de Coutinho3, G. G. B. de Souza3, R. B. de Castilho3, R. L. Cavasso-Filho4, A. F. Lago4 and A. N. de Brito5 Vale do Paraíba University (UNIVAP), São José dos Campos, SP, Brazil Bahia Federal University (UFBA), Barreiras, BA, Brazil 3 Rio de Janeiro Federal University (UFRJ), Rio de Janeiro, RJ, Brazil 4 ABC Federal University (UFABC), Santo André, SP, Brazil 5 Brazilian Synchrotron Light Laboratory (LNLS), Campinas, SP, Brazil 1 2

9 Mass spectra of the fragments produced by the interaction of 150-eV photons with gaseous samples of glycine

Facility: TGM Publication: Monthly Notices of the Royal Astronomical Society 411, 2214 (2011) Funding: LNLS, CNPq, FAPERJ, FAPESP Corresponding author: Sérgio Pilling – sergiopilling@pq.cnpq.br

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SCIENCE HIGHLIGHTS

An extraterrestrial origin of the building blocks of life on Earth – DNA nucleobases included – is a concrete possibility. Scientists have been detecting signs of them in several cosmic environments: comets, meteorites, planet atmospheres and even in the interstellar medium. But these molecules are also destroyed by X-ray and ultraviolet radiation originated from nearby stars. Can they survive enough to reach the surface of planets and moons? Only a quantitative research should clarify that. This important question was answered last year by Brazilian scientists that used synchrotron radiation at the LNLS to simulate the soft X-rays that hits these pre-biotic compounds in the space. The answer is yes, they may survive enough, depending on the conditions. In fact, the data indicated that nucleobases may last for 90 billion years in protoplanetary nebula near young stars.

Do the molecular building blocks of life, such as amino acids and DNA nucleobases, have an extraterrestrial origin? In the last 20 years, amino acids have been found in meteorites; and precursors of nucleobase molecules have been detected in comets and interstellar molecular clouds. Species that are the expected major results from nucleobases photodissociation by cosmic X-ray and ultraviolet radiation have also been observed in interstellar medium. The year of 2009 witnessed the first detection of an amino acid (glycine) in a comet in all times. All of this does not necessarily mean that these prebiotic compounds could have survived long enough in the protoplanetary environment around young stars to be delivered to planets and moons in the remote past (and even today). In the interstellar environment, these molecules are exposed to X-ray and ultraviolet radiation originating from nearby stars and tend to be dissociated by these rays into smaller fragments. So they could be important for pre-biotic chemistry in planets and moons only if a substantial part of them is not destroyed by X-ray and UV during the time of formation of these bodies. The fact seems to be that at least some of them actually do survive that much. This became particularly clear last year after a research led by Sérgio Pilling from the Vale do Paraíba University (UNIVAP), in São José dos Campos, Brazil. A collaboration of scientists from five Brazilian institutions did experiments with synchrotron radiation at the Brazilian Synchrotron Light Laboratory (LNLS, in Campinas, Brazil) and found that some of the pre-biotic molecules present in the cosmic space may survive even the entire lifetime of their host molecular clouds. So yes, these chemicals were really able to reach the pre-biotic Earth in

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meteorites and comets (now, if they have something to do with the origin of life on Earth is another story, for which verification much more research is needed).

Simulating pre-biotic environment

The experiment was a simulation of the action of cosmic soft X-rays of a specific energy (150 eV) on three amino acids (glycine, DL-valine and DLProline) and two nucleobases (uracil, a building block of RNA, and adenine, found in both RNA and DNA). See Figure 1 and 2 for details of the apparatus. In dense molecular clouds and protostellar disks, these substances may occur in either gaseous or solid phases, the latter being part of the small grains that exist in the interstellar material. So tests were made for both solid and gaseous phases (more exactly, gaseous only for glycine and the two nucleobases, due to the physico-chemical characteristics of the samples). The intensities of the X-ray in different cosmic environments vary a lot, differing by many orders of magnitude. As an example, one can take the molecular cloud around the star AFGL 2591, a very studied one situated at 3,000 light-years from Earth. At a distance of 200 au from its central star (one au, astronomic unit, is the average distance between the Earth and the Sun), the flux of X-rays at 150 eV is of about 3 × 106photons/cm2/sec. On the other side, at 25 au from the also widely studied star TW Hya, in the middle of the planetary nebula that surrounds it (176 light-years from Earth), one finds only 3  ×  103 photons/cm2/sec. These systems are interesting as examples because signs of organic prebiotic molecules (the molecules themselves, or their precursors, or the results of their photodissociation) have been found in them in the last years.


DNA nucleobases may survive in outer space for billion of years

Figure 1. Experimental apparatus for the gaseous phase samples. The X-rays were produced by the LNLS synchrotron accelerator (“to beamline” in the figure). The radiation crossed a beam of molecules of the studied sample, came from a vacuum chamber where its solid phase was vaporized to produce the gas (“sample needle”). The X-ray dissociated the sample molecules and the various resulting fragments were determined with a mass spectrometer (the set of mechanisms at the right of the green “acceleration grids”).

Figure 2. Experimental apparatus for the solid phase samples. The sample was built in the shape of a thin film on a substrate. In this case, the resulting fragments could not be measured with the mass spectrometer because they were fixed with the solid sample and could not be made to fly through the “drift tube” (see Figure 1), so the sample was subjected to a beam of infrared radiation during the X-ray exposure to make an absorption spectroscopy measurement (“IR source” and “IR detector”).

A much larger flux is observed in another kind of interstellar environment, the so-called X-ray dominated photodissociation regions (XDRs). These are inner regions of dense molecular clouds where ultraviolet radiation does not penetrate, because they were already completely absorbed by the matter of

the outer shells. In these places, the flux at 150 eV is typically of the order of 3 × 1010 photons/cm2/sec. It is very difficult to reproduce so distinct environments in the laboratory. However, the scientists could infer the lifetimes of the molecules in each of them with a three-step method. First, they measured the amount of each of the main molecular fragments that resulted after the synchrotron X-ray passed through the samples and dissociated their molecules. With these data they could calculate the cross sections for the dissociation of each of the five studied molecules (the second step). The cross section of a specific collisional event is a quantity proportional to the probability that the event occurs, much used because it is directly measurable (in this case, the event is the dissociation of a specific molecule caused by the collision with an X-ray photon). Finally – the third step –, with the cross sections and the X-ray flux taken from the scientific literature as inputs, it is not difficult to calculate the half-life of the molecules, that is, the time necessary to half of them to be dissociated.

They fell on Earth

The results that emerged from all of this have interesting implications. First, the nucleobases are much more stable than the amino acids under X-ray

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SCIENCE HIGHLIGHTS

environment. Their half-lives are two orders of magnitude higher than the latter’s. In fact, in XDRs, where the X-rays are very intense, the half-life of solid glycine is just 70 years; but adenine and uracil half-lives are of 9 × 103 and 2 × 103 years, respectively. This is possible due to the aromatic rings present in

Figure 3. The chemicals used as samples in the experiment. The three at the top are amino acids; the two at the bottom are nucleobases.

the adenine and uracil molecules (see Figure 3), that tends to make them stable. Relatively to the typical times involved in planet formation, some thousand years is a very short period. However, near AFGL 2591 and TW Hya stars the X-ray flux is much lower and, consequently, the half-lives much larger (although the proportions between amino acids and nucleobases half-lives are maintained). In the latter case, near TW Hya, solid glycine half-life is of 7 × 108 years, and solid adenine and uracil half-lives are – and now these values have very interesting implications – of 9 × 1010 and 2 × 1010 years, respectively. Similar results appear for the nucleobases gaseous cases. This is a really large period – the Sun is about 4.6 billion years old and life begun on Earth about 3.7 billion years ago; and the Big-Bang itself happened 1.36 × 1010 years ago! These values certainly must vary from star to star, from nebula to nebula, but these results show that adenine and uracil may last long enough in protoplanetary environment to be delivered to planets and moons. They would be produced in the

Table 1. Photodissociation cross-sections, σph-d, and half-life, t1/2, for the studied amino acids and nucleobases (in gaseous and solid phases) obtained upon exposure to soft X-ray at 150 eV. The three last columns for each phase show the calculated half-life for these compounds in three different astrophysical environments.

Solid phase Samples

σph-d 10–18 cm2

Lab.a (h)

XDRsb (yr)

t1/2 Dense cloudsc (yr)

PPDsd (yr)

Glycine

40

12

70

7 × 105

7 × 108

DL-Valine

96

5.2

30

3 × 105

3 × 108

DL-Proline

13

38.5

200

2 × 106

2 × 109

Adenine

0.3

~1730

9 × 103

9 × 107

9 × 1010

~1.2

~330

2 × 10

2 × 10

2 × 1010

Uracil

3

7

Gas phase Samples

σph-d

XDRsb (yr)

2.6

185

1 × 103

1 × 107

1 × 1010

-

-

-

-

-

10–18 cm2 Glycine DL-Valine DL-Proline

t1/2

Lab.a (h)

Dense cloudsc (yr)

PPDsd (yr)

-

-

-

-

-

Adenine

~0.3

~1730

9 × 103

9 × 107

9 × 1010

Uracil

~0.8

~495

3 × 103

3 × 107

3 × 1010

F150eV = 4 × 1011 photons cm–2 s–1 ~103 erg cm–2 s–1 (off-focus TGM beamline). F150eV ~ 3 × 1010 photons cm–2 s–1 (typical XDR flux in molecular clouds). c F150eV ~ 3 × 106 photons cm–2 s–1 (for AFGL 2591, at 200 au from the X-ray source). d F150eV ~ 3 × 103 photons cm–2 s–1 (for typical T Tauri discs at 25 au into the disc from the central star). a

b

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DNA nucleobases may survive in outer space for billion of years

cosmic space through chemical reactions typical of interstellar environment and eventually they would become part of protoplanetary nebulae. At the beginning of the planets and moons formations, they would be trapped in solid grains, meteoroids and comets that populate this kind of environment. According to the author’s results, in many cases they could survive in this form until the formation of the larger bodies is completed, when they would be delivered over their surfaces.

atmospheres such as Titan’s. However, the sicneitif knowledge does not have a definite answer to that yet. There are many chapters ahead in the fascinating fields of astrobiology and astrochemistry.

But where are the nucleobases?

As nucleobases are more stable than amino acids under X-ray environment, it should be expected that the former should be found more copiously in radioastronomical observations of cometary or molecular clouds. However, what has been observed is exactly the opposite. Indeed, amino acids, including glycine, has been found in meteorites in the last 20 years and, more recently, in comets; but no direct detection of nucleobases in comets or molecular clouds has been successful (although some of their precursors, such as HCN, pyridines, pyrimidines and imidazole were reported). There is no answer to this paradox yet. But what were investigated in the present experiments were the dissociation products. It happens that the abundance of the chemicals is ruled not only by their dissociation by radiation, but also by their process of formation. According to the authors, probably the aswer to the paradox is related to the efficiency of synthesis of these compounds in the interstellar environment, rather than to their dissociation. More researches are needed to verify this hypothesis. Anyway, even if the pre-biotic molecules are not directly found, their signatures may be detected. One of the indirect signs of their existence is the resulting fragments from the dissociation – that were collected in the author’s experiment (Figure 4). Indeed, at least one of the most abundant fragments of adenine and uracil, HCNH+, has been extensively found in the interstellar medium, comets and even in planetary

Figure 4. Mass spectra of the fragments produced by the interaction of 150-eV photons with gaseous samples of glycine (a), adenine (b) and uracil (c). The blue labels in parenthesis indicate possible neutral molecules released together with the cationic species. The red brackets at the right of each figure are the branching ratio that indicate the amount of the parental compounds (glycine, adenine or uracil) that survived to the X-ray bombardment.

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10

On the stabilization of gold nanoparticles over silica-based magnetic supports modi�ied with organosilanes Rafael L. Oliveira1, Daniela Zanchet2,3, Pedro K. Kiyohara4, and Liane M. Rossi1

Instituto de Química, University of São Paulo (USP), SP, Brazil Brazilian Synchrotron Light Laboratory (LNLS), Campinas, SP, Brazil 3 Instituto de Química, State University of Campinas (Unicamp), SP, Brazil 4 Instituto de Física, University of São Paulo (USP), SP, Brazil 1

2

Transmission electron microscopy (TEM) images of (a) Fe3O4@SiO2–NH2–Au and (b) Fe3O4@SiO2–Au

50 nm

50 nm

Facility: XAFS1 Publication: Chemistry – A European Journal 211, 4626 (2011) Funding: FAPESP, CNPq Corresponding author: Liani M. Rossi – lrossi@iq.usp.br

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On the stabilization of gold nanoparticles over silica-based magnetic supports modi�ied with organosilanes

Green chemistry has been taking advantage of nanoscience to establish new cleaner and environmentally friendly catalytic chemical processes in the last years. Studies on gold nanoparticles have shown that they can be very active catalysts for important reactions, such as selective oxidation of alcohols. However, the noble metal is not easy to deal with – it does not attach itself well to silica surface, one of the most used supports to immobilize catalysts. New methods are needed to produce supported gold nanoparticles with size distributions sharp enough to be useful in industrial chemistry. A team of Brazilian researchers managed to bring successfully a solution last year. The secret is to cover silica surface partially with amino (–NH2) groups. This can drastically increase the ability of silica surface to be impregnated with gold. Tests with common alcohol oxidation reactions yielded high selectivity and conversion rates.

Harmful technologies to environment and human health are (happily) becoming less and less tolerable and being substituted by cleaner ones. In chemical industry and scientific laboratories, expressions like “green chemistry” and “green oxidation” reflect the growing preoccupation with the unwelcome side effects of many old synthesis processes. One of the good novelties in this field, are metal nanoparticles that may be used as green catalysts in some of the most important reactions in organic chemistry. One example is the selective oxidation of alcohols to yield products such as aldehydes, ketones, carboxylic acids and their derivatives. But science and technology evolve through complex ways and the best answers are achieved only after many obstacles are overcome. Catalysts should be recovered after the reactions in order to be used again and economically attractive; the currently most used techniques to do it are filtration or centrifugation, which can be less efficient for nanoparticles. Improvements of the methods with nanoparticles pass through the development of easier recovering techniques. Another problem exists. Among the most efficient metal nanoparticles used as catalyst in green oxidations is gold. Well, nanocatalysts are usually immobilized on some “support”, in general larger particles; as for example silica (SiO2). However, gold does not impregnate silica surface easily; the production of silica-supported gold nanoparticles demands special techniques to obtain size distributions sharp enough. Easy ways to turn this process more direct and cheaper are searched by scientists around the world. Some Brazilian researchers lead by Liane Rossi from the University of São Paulo (USP), in Brazil have been

working with a method that solves the first problem, how to recover easily gold catalysts, at least for the reactions they have been working with. Their silica substrate has a core of magnetite (Fe3O4) that is superparamagnetic, so a simple magnetic field may be used to take the nanoparticles off from among the reaction products so that they can be used again. Last year, the team (that involved also the State University of Campinas, Unicamp, and the Brazilian Synchrotron Light Laboratory, LNLS, in Campinas, Brazil), showed how to solve the second problem – to make gold to attach easily to the silica particles. The secret was to functionalize the silica surface with organosilanes, that is, to partially cover it with amino (–NH2) groups. They raise the ability of the support to be impregnated with gold.

Figure 1. The system produced by the authors: gold nanoparticles

attached to the surface of silica (SiO2) partially coated with amino (–NH2) groups; the silica support has a core of magnetite (Fe3O4) for magnetic separation.

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SCIENCE HIGHLIGHTS

Building the supported nanoparticles

So the support for the gold nanoparticles was silica spheres with a magnetite core – usually referred to as “Fe3O4@SiO2”. After the support was synthesized, the next step was to attach amino groups to the silica surface – that is, to functionalize it. There are standard procedures for it, that consist on making the Fe 3O 4@SiO 2 composite to react with a bi-functional molecule that has both an -Si(OCH2CH3)3 group and the desired amino group, such as 3-aminopropyltriethoxysilane (APTES). The resulting system is labeled as Fe3O4@SiO2–NH2. The next step is to attach gold to it. So Fe3O4@SiO2– NH2 was added to an aqueous solution of HAuCl4. Under suitable conditions, the reaction makes gold atoms to attach themselves to the silica surfaces. The support loaded with gold was then separated from the solution, what could be done easily with a magnetic field thanks to the magnetite core. As a matter of fact, one additional procedure was needed after that, to chemically reduce gold by means of a treatment with hydrogen. That was because nonreduced systems produced only excessively broad size distributions nanoparticles under reaction conditions. However, before the reduction was done, it was possible to characterize the obtained systems with several experimental methods.

Laboratory diagnosis

The first set of experiments was done to verify if the amino-functionalized version of the support really could make gold to be attached more efficiently to silica. That demanded a measurement of the amount of gold in the system. A suitable method to

detect small amounts of metal in chemical systems is inductively coupled plasma optical emission spectrometry (ICP OES) that was used by the authors. They could see that the functionalized version was readily loaded with 0.72 wt% of gold, while the nonfunctionalized one was not impregnated with gold. One could only obtain 0.72 wt% of gold in that case by evaporating the whole solvent. Figure 2 shows images of the particles taken with transmission electron microscopy (TEM). On the left picture, there are the amino-functionalized systems. The gold nanoparticles are the small darker spots. One can see that, in the functionalized system, they are attached to magnetite-silica particles, while in the non-functionalized system (at the right) they are mostly dispersed out of the silica support. So it was not a surprise that, when the authors tried the magnetic separation of the catalyst from the aqueous suspension, they could not recover most of the gold particles in the non-functionalized system, while in the functionalized version the magnetic separation worked pretty well. A very important parameter that could also be assessed with the TEM images were the diameters of the gold nanoparticles, of 5.9 nm in average. However, that could be reached only after a chemical reduction of gold with hydrogen gas, as said above. Besides, without this procedure, the size distribution of the gold nanoparticles obtained under reaction conditions was seriously degraded, ranging from 2.1 to 31 nm. Another interesting difference between the two systems – functionalized and non-functionalized – was that before the metal reduction step, in the last one, the oxidation state of gold was Au3+, while the functionalization reaction produced a partial reduction in it, resulting in a lower oxidation state,

Figure 2. Transmission electron microscopy (TEM) images of (a) Fe3O4@SiO2–NH2–Au and (b) Fe3O4@SiO2–Au.

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On the stabilization of gold nanoparticles over silica-based magnetic supports modi�ied with organosilanes

probably Au1+. That could be assessed with X-ray absorption fine structure (XANES) spectroscopy, done at the LNLS facilities, after the solids loaded with gold were separated from the aqueous solution by a magnetic field, but before completing the last step of the synthesis of the supported nanoparticles. XANES, together with a related method, extended X-ray absorption fine structure spectroscopies (EXAFS, also done at the LNLS), allowed also to determine the coordination numbers between gold and their neighbor atoms in the system before and after metal reduction (gold, chlorine, oxygen, nitrogen). That was important to provide clues about which microscopic mechanisms were responsible to the differences in the XANES spectra between the two samples, functionalized and non-functionalized. An analysis of the data gave evidences that what was happening in the functionalized sample was not

simply adsorption of gold in silica, but an interaction between gold and the amino groups attached to the surface. The full understanding of the mechanism shall be reached after more scientific research.

Oxidizing alcohols with the new method

Finally, it was necessary to verify if those nanoparticles really worked well for what they were designed for – to catalyze alcohol oxidation. An efficient catalyst must have good conversion rate (they should oxide most of the alcohol molecules) and good selectivity (no unexpected side products should be released). Tests were done with eight different alcohols, some of them containing other oxygen-sensitive functionalities, such as C=C double bonds. The results, shown in Table 1, indicate that the gold catalyst prepared in the amino-

Table 1. Oxidation of alcohols by the magnetically recoverable Au NP catalyst.

Entry[a]

Substrate

1

Product OH

2

O

O

O OH

O

3

4

O N

+

O

O

Cl O

OH

O

N

+

O

5

OH

7

HO

8

OH

Selectivity[b]

5

95.7

100

5

78.2

99.5

5

73.4

97

6

4.3

100

4

99.8

100

4

99.0

99.0

6

64.1

99.0

4

99.0

99.0

O

HO

6

Conversion[b]

O

O

OH

Cl

p O2 [atm]

O

O

O

[a] Reaction condition: substrate (2 mmol), supported catalyst (50 mg, 2.54 µmol Au), K2CO3 (50 mg), toluene (2mL), 110°C, 6h. [b] Determined by GC.

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SCIENCE HIGHLIGHTS

functionalized support had indeed high conversion rate and selectivity for most of them. Besides, they were fully recoverable: after magnetic separation of the catalyst from the reaction products, an analysis with atomic absorption spectroscopy detected no gold remaining in the products. This kind of reaction must happen in the presence of a base and some of the most used ones were also tested. With no base, the conversion rate was really small. The one that allowed reaching a conversion rate of practically 100% for some substrates was potassium carbonate (K2CO3). Another potentially good candidate, potassium hydroxide (KOH), did not work because it caused corrosion of the silica layer; a

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third one, triethylamine (Et3N), caused metal leaching and the catalyst was deactivated in the middle of the oxidation reaction. At this point, the set of experiments and tests were complete. The authors presented a method to produce gold nanoparticles attached at the silica support surface that allows recovering them easily with a magnetic field after catalytic reactions. The tests with common reactions showed that it is as a workable technique able to make aldehydes and ketones, important products used in chemical industry, by selective oxidation of alcohol; using environmentally friendly reagents, cleaner and faster than traditional synthesis methods.


Sputtering onto liquids: from thin �ilms to nanoparticles

Heberton Wender1, Renato V. Gonçalves2, Adriano F. Feil2, Pedro Migowski3, Fernanda S. Poletto3, Adriana R. Pohlmann3, Jairton Dupont3, Sérgio R. Teixeira2

Brazilian Synchrotron Light Laboratory (LNLS), Campinas, SP, Brazil Instituto de Física, Federal University of Rio Grande do Sul (UFRGS), Porto Alegre, RS, Brazil 3 Instituto de Química, Federal University of Rio Grande do Sul (UFRGS), Porto Alegre, RS, Brazil 1 2

11 From Thin Films to Nanoparticles

Facility: SAXS2 Publication: The Journal of Physical Chemistry 115, 16362 (2011) Funding: CAPES, CNPq Corresponding authors: Herberton Wender – hbtwender@gmail.com Sérgio T. Teixeira – durao@if.ufrgs.br

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SCIENCE HIGHLIGHTS

When scientists develop cleaner ways to synthesize colloidal metal nanoparticles – that have a wide range of applications in research and industry –, they usually work on the external chemicals needed in the synthesis processes, such as solvents and reducing agents. But two years ago a new method was introduced without using such substances: sputtering atoms onto the liquid substrate (with which one wants to form the colloid). The novel technique is at its very beginning and the scienti�ic literature still lacks some basic knowledge important to improve it, such as comparative data between different systems or insights about the physicochemical mechanisms behind the nanoparticles formation. Some of these gaps started to be �illed last year when a team of physicists and chemists published a paper with the �irst guesses about the underlying phenomena and comparisons between different liquid substrates.

Sputtering onto liquids: from thin �ilms to nanoparticles

Among the numerous interesting and useful physical systems studied in nanoscience, there are colloidal metal nanoparticles – that is, metal nanoparticles dispersed in a liquid so as to form a colloid. The list of the application areas is impressive: among them are biomedicine, electronics, optoelectronics, nonlinear optics, solar energy conversion, catalysis, luminescence and industrial processes for the fabrication of cosmetics, varnishes and paints. A substantial part of the investigations about these nanoparticles consists in searching for cleaner methods to produce them. That may be not so easy, because the traditional techniques use chemical reactions involving reducing agents and solvents that may be not environmentally friendly. So scientists all over the world search for methods to be used in the synthesis processes that do not contribute to the greenhouse effect or harm the human health. As a matter of fact, the best solution is to avoid to use solvents and reducing agents. In 2010 a new method has been introduced that simply avoids such external chemicals: bombarding a liquid substrate with a lot of individual metal atoms. The atoms are obtained by “sputtering”, that means, they are expelled from a solid bulk metal by means of collisions with other particles (for example, argon ions from an electric glow discharge). In general, sputtering is used to make thin films grown on a solid substrate (which is useful in several areas such as electronics); however, under certain conditions, atoms sputtered into a liquid may naturally agglomerate to form the desired metal nanoparticles instead of a thin film on its surface.

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The study about this new technique is at its very beginning and it is still necessary to accumulate some basic knowledge about its details in the scientific literature. Indeed, until last year no scientific work presented comparative studies between different systems; neither there were publications about the physical mechanisms involving the formation of the nanoparticles. These gaps started to be filled with a paper released in the middle of 2011 by a team of Brazilian physicists and chemists from the Rio Grande do Sul Federal University (UFRGS), in Porto Alegre, and the Brazilian Synchrotron Light Laboratory (LNLS), in Campinas, lead by Heberton Wender and Sérgio Teixeira, from UFRGS. They compared what happens when silver atoms are sputtered onto three kinds of vegetable oils: castor oil (which is common in Brazilian Northeast among other tropical regions), canola oil and caprylic/capric triglyceride (CCT) oil. The information that emerged from this crossed approach allowed them to guess some physico-chemical processes probably responsible for the formation of either nanoparticles or thin films, depending on the conditions.

Thin �ilms x nanoparticles

The scientists concluded that there were two main parameters that determined which of these two systems were formed. The first one was the discharge voltage applied in the sputtering apparatus. In their experiments, sputtering were produced by collisions of Ar ions from an electric discharge with bulk silver, so as to provide free silver atoms that were driven into the liquid. A higher discharge voltage produces atoms with more kinetic energy. What the authors observed was that higher voltages made nanoparticle formation


Sputtering onto liquids: from thin �ilms to nanoparticles

easier and low voltages made thin films tend to appear, as schematized in Table 1. The second parameter was the surface coordination ability of the oils. Coordination ability is related to the ability of a molecule, or some part of a molecule, to bind to other atoms. As will be shown below, the oil molecules at the liquid surface are not randomly oriented, but have predominantly their apolar regions pointing to the surface, while the polar regions sink into the liquid bulk. In general different regions of an organic molecule have different coordination abilities; so in this case the coordination abilities at the surface of the liquid are dinstinct and we may Table 1. Summary of AgNPs or AgTFs formation as a function of the discharge voltage and of the oil chosen as the liquid substrate.

Oil

AgTFs formation (V)

AgNPs formation (V)

Castor

240

≥ 280

Canola

240 to 320

≥ 420

CCT

240 to 420

≥ 490

talk of “surface coordination ability”. The scientists’ results indicated that higher surface coordination ability meant a higher tendency to form nanoparticles instead of thin films. These conclusions were reached by using the results of the characterization of the obtained thin films and nanoparticles. The latter were imaged with transmission electron microscopy (TEM), from which it was possible to access the mean diameter of the particles. Figure 1a shows TEM images of nanoparticles in castor oil with average diameter of 5.5 nm, obtained with a discharge voltage of 320 V. Size is a very important parameter, because the efficiency of any nanosystem for whatever they are designed for depends crucially on their sizes. Images of the thin films, on the other hand, were made with optical photographs in bright field (Figure 1b and 1c, respectively for canola and CCT oils, 320 V). Note that both films present cracks, but they are more abundant in canola oil. Other nanoparticles’ characteristics, such as their shape (revealed to be mainly spherical) and their size

Figure 1. (a) A representative transmission electron microscopy (TEM) image of the silver nanoparticles in castor oil sputtered by silver atoms. Top-view optical photographs in bright field of silver thin films on the surface of canola oil (b) and CCT oil (c). The three structures were formed after sputtering at 320 V for 150 seconds. SAXS data and fittings (d) and size distributions (e) of silver nanoparticles obtained after 150 s of sputtering onto castor oil with different discharge voltages.

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SCIENCE HIGHLIGHTS

distributions as a function of the discharge voltage used in sputtering were determined by means of small-angle X-ray scattering (SAXS, Figure 1d-e) performed at the LNLS and ultraviolet-visible (UV-Vis) absorption spectra. Important information could be inferred from these data: the larger the discharge voltage, the larger the mean sizes of the silver nanoparticles were.

The underlying physical phenomena

To understand the main authors’ ideas about how nanoparticles and thin films are formed, it is important first to consider the molecular structure of the oils depicted in Figure 2. They are tryglicerides, composed of three fatty acids (labeled as “R” or “radical” linked to a glycerol molecule (depicted at the top left). The content in each oil – that is, the meaning of “R” – is listed. The important fact here is

that each molecule has a polar region, situated in the glycerol region, and an apolar part, that correspond to the fatty acid chains. As the positive and negative poles of the polar regions of different molecules attract each other, it is natural to assume that the molecules at the surface of the liquid will predominantly have the apolar part at the surface and the polar part under it, pointing to the liquid bulk. See also Figure 3, where the fatty acid chains are represented by straight lines in the molecules. With this knowledge, it is possible to understand the reasons for the different behavior of the three oils. Consider firstly castor oil, the one that most easily formed nanoparticles. Figure 2 shows that its most abundant fatty acid molecule is ricinoleic acid. This fatty acid has something that none of the listed others have: a hydroxyl group in its carbon chain – that will be, according to the previous discussion, mostly at the liquid surface. Because of this hydroxyl group, the coordination ability of the surface of castor

Figure 2. General structures and composition of the three vegetable oils used as the liquid substrate for the sputtering of silver atoms.

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Sputtering onto liquids: from thin �ilms to nanoparticles

Figure 3. Schematic illustration for the formation of silver nanoparticles or thin films by sputtering deposition of silver onto liquids. The straight lines in the oil molecules represent the fatty acid chains.

oil should be the greatest of all three used oils. The second most coordinated should be canola oil, that has unsaturated carbon chains. The last one, CCT oil, is almost completely uncoordinated because their fatty acids have only saturated alkyl chains. And why does surface coordination ability mean a higher probability to obtain nanoparticles and a lower to have thin films? The silver atoms tends to bind to the functional groups, so the more coordinated the surface, the less the diffusion of atoms (or nucleus, or nanoclusters) on the oil surface will be. And, if the formed nanoparticles can diffuse easily through the surface, they will easily collide and interact to form thin films. This is why the authors consider that poorly coordinating surfaces tend to form thin films over them, while strongly coordinating surfaces tend to stabilize the nanoparticles against their coalescence in films. See Figure 3. At the same time, this mechanism is also influenced by variations on the discharge voltage in the sputtering apparatus. The authors made tests in the range from 240 to 490 V. The proposed mechanism is as follows. A higher voltage makes more atoms arrive at the liquid surface with more energy. With

higher energies these atoms diffuse easier through the surface and accelerates the nucleation processes that form the nanoparticles. After the concentration of nanoparticles at the surface reaches a certain critical value, they start to precipitate downwards into the liquid bulk, while new ones could hence be formed at the surface from newly arriving sputtered atoms. So in this case the effect of a higher diffusivity is opposite to the previous situation (in which the surface coordination ability was varied). If the voltage was high enough, nanoparticles could be formed even in the surfaces of less coordination ability. Indeed, although thin films appeared in canola and CCT oils (the more coordinated ones) through the whole 240-490 V range, for higher voltages there appeared nanoparticles under the films (in a smaller amount than in castor oil, as a matter of fact). All this information, grouped together, forms an important contribution to the basic knowledge and know-how that are growing in the scientific literature since 2010 about colloidal metal nanoparticles produced by sputtering onto liquids. In the future, it may allow building them in a clean way, without any chemicals more dangerous than single vegetable oils.

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12

Magnetic thin �ilms

C. E. Rodríguez-Torres1, F. Golmar2, M. Ziese3, P. Esquinazi3, and S. P. Heluani4 IFLP-CONICET and Departamento de Física, Facultad de Ciencias Exactas, La Plata National University, La Plata, Argentina 2 CIC nanoGUNE Consolider, Donostia, Spain 3 Division of Superconductivity and Magnetism, University of Leipzig, Germany 4 Departamento de Física, FCEyT, Tucumán National University, Tucumán, Argentina

1

Zn (left) and Fe (right) K-edge XANES, taken for film deposited at 10–5 mbar for two different incidence angles.

Facilities: XRF, XAFS2 Publication: Physical Review B 84, 064404 (2011) Funding: LNLS, CIUNT, ANPCyT, PROALAR, DFG, CONICET Corresponding author: C. E. Rodríguez-Torres

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Magnetic thin �ilms

Zinc ferrite (ZnFe2O4) does not have a net magnetic moment and becomes antiferromagnetic at very low temperatures, below 10 K. Or, more precisely, its bulk form. When nanosized, it acquires a room temperature magnetization of the same order of magnitude than a common magnetic bar. How can it be? Scientists have some hypotheses but nobody still knows exactly how these new magnetic properties work nor how to control them. The basic idea is that it has something to do with small defects in the crystalline structure which depend on the sample synthesis process. These defects may be iron/zinc atoms with modi�ied coordination numbers or oxygen atom vacancies. Last year, scientists studied zinc ferrite thin �ilms at the LNLS facilities and gave further support to these two hypotheses and found other mechanisms. Besides, they concluded that zinc/iron nonequilibrum and oxygen vacancies are related; consequently, in this case one might control the sample magnetic properties by monitoring the oxygen pressure during its synthesis process (that in�luences the number of oxygen vacancies).

Magnetic thin �ilms

Nanosized materials may have properties radically different from their bulk forms. This is one of the most fascinating features of nanoscience, which make known materials be in fact new materials. One striking example is zinc ferrite (ZnFe2O4). In its bulk form, it does not have any net magnetic moment. However, zinc ferrite thin films (some tens of nanometers thick) may have a magnetization at room temperature comparable to common magnetic bars! Obviously, this specific phenomenon is quite attractive for scientific research, both to understand deeper the fundamental mechanisms of magnetism and to search for applications – in particular, zinc ferrite has suitable properties for spintronics, a raising branch of signal transmission research in which signals are carried by spin waves instead of electrons movements as in common electronics. It is still not well known why zinc ferrite acquires magnetic properties when one or more of its dimensions are nanosized. As a matter of fact, bulk ZnFe2O4 becomes antiferromagnetic at very low temperature, below about 10 Kelvin. But antiferromagnetic materials have their magnetic moments aligned but in opposite directions, so even at these temperatures the net macroscopic magnetic moment is still zero. A clearer understanding about the mystery came last year, after some experiments done by a group of Argentinian, Spanish and German scientists at the Brazilian Synchrotron Light Laboratory (LNLS), in Campinas, Brazil. Their samples had magnetizations of up to 360 emu/cm 3, comparable to common magnetic bars. In reality, the accumulated data in

the scientific literature is already enough to suggest some basic hypotheses about the physical phenomena underlying the effect. The experimental evidences found by the researchers not only gave further support to some of them but also showed that there are other mechanisms involved, revealing that zinc ferrite thin films have a richer structure than previously thought. In particular, the behavior of ZnFe2O4 is related to small defects in its atomic structure that depends upon the method used to synthesize the thin films. The defects are due to rearrangements of some zinc and iron atoms in the crystalline lattices and to some vacancies of oxygen atoms. The authors also found that these small changes depended on the oxygen pressure used in the process of growing the film. As a result, the magnetic and transport properties of the material might be controlled by selecting the oxygen pressure.

Macroscopic magnetization emerging from microscopic disorders

To understand their work better, it is necessary to know something about the zinc ferrite structure. It has a spinel structure, shown in Figure 1. As indicated, in the bulk material, all the zinc atoms are at tetrahedral sites (in green) while the iron atoms (in blue) are at octahedral sites. Oxygen atoms are shown in red. As pointed out above, at low temperatures the bulk material is antiferromagnetic, that is, the magnetic moments of iron atoms are either in one or in the opposite direction, providing a zero net magnetic moment.

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In spinels, antiferromagnetism raises by means of the so-called superexchange mechanism. As there are oxygen atoms between the iron atoms, the interaction between “neighbor” irons which make them to have opposed magnetic moments is mediated by the interposed oxygen atoms. The superexchange interaction strength depends on the geometry involving the two iron atoms and the intermediate oxygen. Figure 1 shows that there are some different geometry in the same crystal. See the atom triads indicated in the figure: ABC, CDE and ACF. Each one forms a different angle. The superexchange interaction is stronger when the angle is closer to 180° (that is, ABC). In the bulk form, however, neighbor irons form with oxygen the triad CDE. However, several works have suggested that, in its nanosized versions, equilibrium between zinc and iron is broken: some iron atoms appears in tetrahedral sites and some zinc atoms are in octahedral sites. Then, different geometries other than CDE raises between neighbor iron atoms (including the strongerly interactive ABC). This alters the longrange magnetic ordering and consequently has drastic effects in the sample macroscopic magnetic behavior. This is the basic idea. But the precise mechanism through which the nonequilibrium lead to a macroscopic net magnetic momentum remained

unknown. Indeed, in 2009 it became clear that the hypothesis above might not be the whole story. Scientists found evidences that oxygen vacancies also influenced the magnetic behavior of zinc ferrite thin films. In fact, there were already other evidences that small defects in crystalline structures could trigger magnetic order in some materials such as some oxides and graphite.

The �irst mechanism: breaking zinc/iron equilibrium

To put these pieces together and to clarify such ideas, scientists had to use a technique sensible to small changes of zinc and iron distribution in the crystal. In fact polarized X-rays may be a good probe for that. The study of the absorption of polarized X-rays with frequencies related to the energy levels of the atoms that constitute the material is the basis of the so-called X-ray absorption near-edge structure (XANES) spectroscopy. The authors used this technique together with another one, also with X-rays, called grazingincidence X-ray fluorescence (GIXRF) that may provide information about composition, thickness and density of thin films, complementary to XANES data. Both of the methods were performed at the LNLS.

Diagram 1. At the top: superexchange interaction in bulk zinc

Figure 1. Schematic spinel structure for bulk ZnFe2O4. The tetrahedral sites are colored in green. In nanosized forms (as in thin films), there are also some zinc irons in octahedral sites and iron atoms in tetrahedral sites, as well as oxygen vacancies and some Fe+3 atoms. Source: Adapted from the Wikipedia – http:// en.wikipedia.org/wiki/File:Spinel.GIF

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ferrite crystalline structure. Neighbor iron atom spins are always antiparallel. At the bottom: in thin film zinc ferrite. Neighbor iron atom spins are antiparallel when one of them is in a tetrahedral site and the other in a octahedral site. This stronger interaction may force neighbor irons in octahedral sites to be parallel moments, as shown. The iron atom marked with a “*” has to “choose” if it is antiparallel to his tetrahedric or to his octahedric neighbor. It chooses the tetrahedric, because its superexchange interaction is stronger with it. Source: Adapted from the Wikipedia – http:// en.wikipedia.org/wiki/File:Spinel.GIF


Magnetic thin �ilms

Their studies indicated that part of the iron atoms in zinc ferrite thin films was located at tetrahedral sites, although in its bulk form they are at octahedral ones. Some works in the scientific literature with samples prepared in different ways indicated that there was an inversion between iron and zinc atoms – the first going from octahedral to tetrahedral sites and the second making the inverse change. That was not what was happening in the author’s samples. More iron went to tetrahedral sites than zinc to octahedral ones. Thus, in thin films it is possible to have neighbor iron atoms in the ABC geometry. In this situation, the exchange interaction is stronger. So, when iron atom magnetic moments in ABC-type triads become antiparallel, this may force iron atom moments in CDE-type triads to become parallel (Diagram 1). Thus, part of the iron atoms behaves as in a ferromagnetic material and the magnetic moment does not cancel out in the whole thin film. As a result, a net magnetic moment arises.

The second mechanism: oxygen vacancies

These effects depend on the thin film synthesis method. The films were fabricated by pulsed laser

deposition (PLD), a technique in which a laser hits a target and the target atoms are deposited onto a substrate. The substrate in this case was made of MgO. In particular, the reactions were performed in the presence of oxygen at certain pressures (which provided the oxygen atoms to ZnFe2O4). The researchers made the pressure to vary from 10–5 to 10–1 mbar. They noticed that the nonequilibrium between iron and zinc was larger for the lowest oxygen pressure. Did it mean that this nonequilibrium had something to do with oxygen vacancies in the crystalline structure of the film? In order to test this hypothesis, the scientists varied the incidence angle of the X-rays in XANES technique. Smaller incidence angles probed more superficial layers of the nanofilm, while larger angles probed deeper layers. So what they did was to analyze how the film properties varied as a function of depth. If oxygen vacancies were really an important factor, then there should be more equilibrium between zinc and iron atoms in the superficial layers than in the deepest ones, because the formers are more easily reached by the oxygen atoms in the synthesis process and so they have fewer vacancies. And that was exactly what the authors saw. In Figure 2, one can see that the 4 nm curve is closer to the bulk (ferrite) curve, and the 35 nm curve is more

Figure 2. Zn (left) and Fe (right) K-edge XANES, taken for film deposited at 10–5 mbar for two different incidence angles, 0.23° and 0.38°. These angles correspond to a depth probe of 5 nm and 35 nm, respectively. For iron (right), the 5 nm curves are closer to the bulk zinc ferrite curves (in green), as discussed in the main text.

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SCIENCE HIGHLIGHTS

Figure 3. Zn (left) and Fe (right) K-edge XANES with incident angle of 0.38° for films deposited at different oxygen pressures. ZFO1: 10–5 mbar; ZFO2: 10–4 mbar; ZFO5: 10–1 mbar. “Ferrite” stands for the bulk zinc ferrite.

distant. This suggests a very interesting possibility: one might control the magnetic properties of zinc ferrite thin films by controlling the oxygen pressure in the synthesis process. That opens room to more controllable and so more precise experimental studies that might clarify even further how zinc ferrite thin films magnetism arises.

Third mechanism: changing in oxidation numbers

The phenomena explained above are not the only one that may contribute to the net magnetic moment. The authors could distinguish one more. In Figure 3, on the right, the XANES energy were tuned to distinguish among iron atom electronic properties. The edge peak for low oxygen pressure (10–5 mbar, sample “ZFO1”) were shifted to the left respect to the other pressures. That indicates the presence of iron atoms with another oxidation state – probably, Fe2+,

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instead of Fe3+. The exchange interaction between atoms with different oxidation states has different strengths, so the presence of Fe2+ in the crystalline structure should result in more nonequilibrium between opposed magnetic moments. So this contributes to increase even more the sample net magnetic moment. What is the final issue? Back to the oxygen vacancies, they should theoretically lead to another effect in the thin film microstructure. In the absence of an oxygen atom, the exchange interaction between the neighbor iron atoms would not hold (recall that this interaction is mediated by oxygen) and the magnetic moment of the two irons would be uncorrelated. So, part of the iron magnetic moments should not be correlated neither by antiferromagnetism nor by ferromagnetism – they should form a state similar to a spin glass. Zinc ferrite thin film structure may be richer than previously thought.


Electrochemical sensing with carbon nanotubes

M. Lorena Cortez1,2, Marcelo Ceolín3, Omar Azzaroni3, and Fernando Battaglini1 INQUIMAE, Departamento de Química Inorgânica, Analítica y Química Física, Facultad de Ciências Exactas y Naturales, Buenos Aires University, Argentina 2 PINMATE, Departamento de Industrias, Facultad de Ciencias Exactas y Naturales, Buenos Aiees University, Buenos Aires, Argentina 3 Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas, Departamento de Química, Facultad de Ciencias Exactas, La Plata National University, CONICET, La Plata, Argentina 1

13 Scheme of polyelectrolytesurfactant lamellar assembly

Facility: XRD2 Publication: Analytical Chemistry 83, 8011 (2011) Corresponding author: Fernando Battaglini – battagli@qi.fcen.uba.ar

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SCIENCE HIGHLIGHTS

Electrochemical sensing platforms are used in scienti�ic research, industry and other areas to measure concentrations of chemicals. Most of the research to improve the instrumentation ef�iciency in this area is focused on the electrode-analyte interface, in particular by seeking for suitable materials to cover the electrode surface. Polyelectrolyte-surfactants complexes are convenient for this purpose, because they have good electrocatalytical properties and assemble spontaneously in multilayer thin �ilms. Last year, two teams of Argentinian researchers managed to add carbon nanotubes to a double complex of this kind and the result had very good properties. Carbon nanotubes also have very good electrocatalytical characteristics but they do not adsorb on graphite easily; the polyelectrolyte-surfactant �ilm acted as glue that kept the nanotubes attached to the electrode. The resulting system was more ef�icient; as an example, it allowed measurement of dopamine concentration, which did not happen without the nanotubes.

Electrochemical sensing with carbon nanotubes

Many people are familiarized with those devices that show in a screen the proportion of, say, glucose in blood just by putting a blood drop on a small strip. In industry and scientific research, these “electrochemical sensing platforms” are much used for many other purposes and do not only detect, but also measures small concentrations of chemicals. Consistently, improvements on their efficiency and on the range of detectable substances are also widely searched for. In these systems, the sample to be analyzed is put in contact with an electrode and the chemical reaction between them causes an electric signal to be detected by an electronic system that converts it to readable data. So the central issue is the interaction between the sample and the electrode. As this interaction depends fundamentally on the nature of the electrode outer molecular layers, most of the current research about this subject focus on modifying its surface. A common way to do this is just by covering the electrode with suitable material thin films. During the last years, it turned out that surfactants have good performance as interfaces for the widely used graphite electrodes, partially because they automatically assemble themselves in layered structures. Things work even better if the surfactants are associated with polyelectrolytes so as to form a layered supramolecular structure over the electrode. Both components contribute with interesting characteristics: polyelectrolytes provide mechanical strength and thermal stability; and surfactants keep their ability to autoassemble in layered films. Scientists are currently seeking for good surfactant-

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polyelectrolytes combinations to make new and more efficient electrochemical sensing platforms. Last year, researchers from the Buenos Aires University and the La Plata University, in Argentina, found an efficient surfactant-polyelectrolyte system that have some promising features. Firstly, they are easily handled and applied on graphite surfaces. That avoids two important problems with the currently researched surfactants: in general they do not adsorb to the most used substracts in this area and, when they do, the process of building a multilayer covering is too time-consuming. Secondly, the new molecular complex forms a nanostructured scaffold that retains negative sample ions in their matrix. This is important to provide good detection efficiency, because the analyte is kept in contact with the electrode long enough to produce a good electrical signal. Another interesting feature is that the complex might be further modified, opening the possibility of testing several new systems. Indeed, in a second moment the scientists associated them with carbon nanotubes, which enhanced the electrocatalytic properties of the system. The used surfactant was sodium dodecyl suulfate (SDS) and the polyelectrolyte was poly(allylamine) (PA). When they are mixed, they spontaneously form colloidal particles dispersed in the solvent. When this dispersion is dropped onto a graphite substrate, it reassembles itself as a multilayered film over the surface. With X-ray reflectometry (XRR), performed at the Brazilian Synchrotron Light Laboratory (LNLS), the average distance between neighbor layers were measured as 13,86 nm. Fig. 1 shows a model of the obtained structure. The system characteristics were assessed with “electrochemical probes”, that is, electrolytes which interaction with the system provide information


Electrochemical sensing with carbon nanotubes

Figure 1. Scheme of polyelectrolyte-surfactant lamellar assembly.

The sodium dodecyl sulfate molecules have an ionic head and a hydrophobic alkyl tail (in green). The complex is composed of alternate ionic and alkane layers; the ionic layer corresponding to the polyelectrolyte molecules plus the surfactant ionic heads.

Figure 2. Cyclic voltammetry for (a) dopamine and (b) ascorbic acid at a bare graphite electrode (thin line); at an electrode covered by a poly(allylamine)–sodium dodecyl sulfate (PA-DS) multilayer (dashed line); and by PA-DS-CNT (bold line). CNT stands for carbon nanotube; E stands for the applied voltage; j for the measured current. Note the improvement caused by the presence of the nanotubes.

about their performance and some relevant physicochemical phenomena. Two of the most used probes for this aim are ferrocyanide, [Fe (CN)6]4–, and Hexaammineruthenium, [Ru (NH 3)6]3+. The authors used these and two others, dopamine (a neurotransmissor) and ascorbic acid. These last two are chemicals also important for biological and medical applications. They are interesting because there is a known problem to be solved: when they interact with bare graphite electrodes, they are

oxidized at too high overpotentials (the external potential that must be applied to the system to work), which make the research difficult. Several methods were introduced to decrease the overpotential. So it was interesting to see if the new system might do it. When an electrochemical probe is applied to the electrode, the chemical reaction between the electrolyte and the electrode material produces an electric current, just when it is used to detect some chemical. The current was measured while an applied potential was varied cyclically (that is, with cyclic voltammetry). In cyclic voltammetry, the resulting graph shape details contain information about the characteristics of the system. A typical example is shown in Fig. 2. The results without carbon nanotubes for [Fe (CN)6]4– and [Ru (NH3)6]3+ indicated that the electrolyte ions are diffused inside the polyelectrolytesurfactant thin film. For dopamine and ascorbic acid, the necessary overpotential was slightly decreased as compared to bare graphite; however, no peaks were observed, even at overpotential of 200 mV. The system would be useful for detection of these substances only if the peaks appeared. This problem was solved with a further improvement. The authors noticed that the polyelectrolyte, sodium dodecyl sulfate, is also frequently used to disperse carbon nanotubes in aqueous solution. So maybe carbon nanotubes could be associated to the polyelectrolyte-surfactant complex to build a more complex structure. Carbon nanotubes are known to have excellent electrocatalytic properties, so the possibility that such triple system might be useful to electrochemical sensing was promising. The authors should just use SDS with carbon nanotubes instead of SDS alone when synthesizing the thin films. Indeed, carbon nanotubes were incorporated very well in the thin film. In reality, in this new case the polyelectrolyte-surfactant complex acted as a supramolecular glue that kept the carbon nanotubes attached to the graphite electrode. And more, their presence did not perturb the lamellar structure neither the spacing between the layers. As this is a central issue, a detailed study of the film structure was made, with X-ray reflectivity and with grazingincidence small-angle X-ray scattering (GISAXS), also performed at the LNLS. In GISAXS, the X-ray are shined on the sample at a very low angle (in this case, 0.27°), in order to assess only the most external molecular layers. The results also showed that the film is formed by several microdomains, slightly misaligned but each individual microdomain has well-oriented lamellar structures.

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SCIENCE HIGHLIGHTS

When applied to dopamine and ascorbic acid, the results were much better than the double system without carbon nanotubes, as depicted in Fig. 2. The electric current response was much higher and much richer structures appeared in the cyclic voltammetry graph, including the peaks. The system also behaved very well for quantitative analysis. A linear relationship between the concentration of the chemicals and the produced electric current in the concentration range from 10 to 200 μM was observed, which is very good to calibrate measurement devices. The detection limit was 6 μM; however, with other methods, such as differential pulse voltammetry, dopamine could be detected at a concentration of just 2.5 μM.

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There may be other modifications besides carbon nanotubes incorporation that could present good electrochemical response. The next step is to investigate what more can be done with the polyelectrolyte-surfactant complex used by the authors. Actually the authors are working on some new systems, one of them incorporating gold nanoparticles to the complex. The original work was published in Analytical Chemistry 83, 8011 (2011) by M. Lorena Cortez, Marcelo Ceolín, Omar Azzaroni and Fernando Battaglini. All figures were taken from the original article above.


Synchrotron Radiation X-Ray Micro�luorescence Reveals Polarized Distribution of Atomic Elements during Differentiation of Pluripotent Stem Cells

Simone C. Cardoso1, Mariana P. Stelling2,3, Bruna S. Paulsen2,3, Stevens K. Rehen2,3

Instituto de Física, Federal University of Rio de Janeiro, Brazil Instituto de Ciências Biomédicas, Federal University of Rio de Janeiro, Brazil 3 Hospital Universitário Clementino Fraga Filho, Federal University of Rio de Janeiro, Brazil 1 2

14 Maps showing trace element distribution in human embryoid bodies

Facility: XRF Publication: PLoS ONE 6, e29244-1 (2011) Funding: CNPq, BNDES, FAPERJ, CAPES Corresponding author: Stevens Rehen – srehen@lance-ufrj.org

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SCIENCE HIGHLIGHTS

The mechanisms through which embryonic cells differentiate into the several biological tissues are still unclear. Knowledge about them should provide precious information about treatment of neural injuries or diseases like Alzheimer’s or Parkinson’s. A new investigation method in this area was introduced, using synchrotron light as a probe to assess element distribution changes in embryoid bodies during neural differentiation. X-ray �luorescence spectroscopy (XRF) allowed determination of new data about trace element polarization and concentration along the differentiation process. Observations were made in human and murine cells and indicated that the element distribution presents self-organization at the atomic level during the differentiation. A new method to study stem cells neural differentiation with synchrotron light has been introduced; this allowed to characterize the pluripotent state towards neural differentiated state through analysis distributionof trace elements. The original work was published in PLoS ONE 6, e29244-1 (2011) by Simone C. Cardoso, Mariana P. Stelling, Bruna S. Paulsen and Stevens K. Rehen. All figures were taken from the original article above.

Studying stem cells with synchrotron light

Synchrotron light is useful for a large variety of scientific applications, from nanoscience to astrobiology, from microelectronics to paleontology. Last year a team of Brazilian scientists discovered one more utility: studies about stem cell differentiation into neuron tissues. Researches in this area have being made in connection with medical treatment of neuron injuries or diseases like Alzheimer’s and Parkinson’s and the authors introduced a new promising experimental method to investigate the phenomenon. Embryonic stem cells are pluripotent and can differentiate into the several biological tissues to form an individual during embryonic development. In some circumstances, adult cells may be artificially induced to recover their pluripotency and so may be used to produce tissues or cells for medical purposes or for scientific research. However, it is still not known why and how pluripotent cells do such extraordinary job. In order to understand this mystery, what scientists have to do is to observe, as most detailed and carefully as possible, what happens with the cells during differentiation process and then build models using the obtained data. The Brazilian researchers, lead by Stevens Rehen from the Federal University of Rio de Janeiro, showed that synchrotron light can be used as a probe to detect changes in trace chemical elements distribution in

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embryoid bodies during the differentiation process that forms neurons. It was the first time that a so detailed study was carried out for pluripotent stem cell neural differentiation.

Stem cells in a synchrotron lab

Synchrotron laboratories have a number of experimental apparatuses that take advantage of the synchrotron light produced by an accelerator. The authors used X-ray fluorescence spectroscopy (XRF) at the Brazilian Synchrotron Light Laboratory (LNLS) in Campinas, Brazil. This technique is sensible to specific chemical element concentrations and so might be used to track them along the differentiation. The distribution of these elements, especially phosphorous, sulfur, copper and zinc, present interesting changes during the process and that may provide precious and still unknown information about it. There are other available techniques that allow determination of trace elements distribution in biological samples, but most of them use high vacuum systems, which may cause undesired changes in the cells, and have spatial resolution limitations. So the first thing to do was to see if exposure to synchrotron radiation did not damage the cells. Fig 1 shows two XRF spectra, one after a shorter exposure of 100 seconds and the second after 1,000 seconds. They are practically indistinguishable, so the radiation does not alter the embryoid bodies structure – at least at the level of XRF sensitivity, that is just what is needed for the method to be suitable to study stem cells. The authors submitted human and murine embryoid bodies to this experiment. They started from some pre-prepared cultures of both embryonic and induced pluripotent stem cells. Firstly, the cultures were let to develop during 4 (for the mouse case) or 7 days (human) so as to form, each one, an embryoid body, a small aggregate of pluripotent cells. From the


Synchrotron radiation x-ray micro�luorescence reveals polarized distribution of atomic elements during differentiation of pluripotent stem cells

Figure 1. Typical XRF spectra from murine embryoid body. A) Standard spectrum obtained after 100 seconds of exposure. B) Spectrum obtained from the same area as A after 1000 seconds of exposure. Both spectra are very similar, which shows that embryonic bodies are not altered at the level of XRF sensitivity. Beam Area: 20x20µm.

several aggregates thus obtained, one group was let to differentiate naturally (the scientists called them “control EB”) and another group was treated with retinoic acid, that induces the formation of neurons (“neuro EB”). The two groups were then analyzed with XRF. By comparing the two sets of results, the researchers could observe what changes in the development were exclusive of neural differentiation.

Self-organization

Among the chemical elements chosen to be detected with XRF, the ones with the most interesting behavior were phosphorous (P), sulfur (S), copper (Cu) and zinc (Zn). This is totally coherent with the fact that these elements play important roles in cell

development and in neuron physiology. Copper and zinc, among other metals, are known to be abundant in neurons. Phosphorous and sulfur are important for cell metabolism in general and are present in nucleic acid and protein composition. The most striking feature observed in the data was a concentration of P and S on one side of the embryoid body of the neuro EB. It was not a concentration on one side of each cell but in the embryoid body as a whole – technically, these elements presented “polarization”. This is shown in the map of Fig. 2, in which the colors represent the degree of concentration of each element. For human cells, the polarization was also detected with some chemical markers, as in Fig 3. Some more experiments ruled out other possible phenomena else than a real polarization that could cause such patterns (the higher concentration in one region could occur just because there were more cells there, produced by eventual variations on the local cell density, or by local cell proliferation or death). A more quantitative approach is obtained by transforming the heat map numerical matrix in a left-right intensity analysis, such as the one in Fig. 4. One can easily see the polarization for sulfur and phosphorous for mouse cells in the “8 days neuro” embryoid body. Human and murine cells have some distinct characteristics: in human embryoid bodies, zinc also has a polarization, although inverse, and polarization is found also in the early stages (7 days). These differences may be due to intrinsic specific characteristics of the two species, but the presence of polarization of these elements in both of them indicates that it is linked to neuron differentiation in a broader sense. Another interesting observation was that copper and zinc contents increase after the differentiation. For mouse cells, the neuro-enriched embryoid body (8 days) has 2.6 times more copper than the 4 days EB. Neural tissues are enriched with metallic elements such as copper, zinc and iron. The new data indicates that metal accumulation may be an early event in neuron differentiation. All these data raises the question: once we know that phosphorous and sulfur have peculiar distributions in neuronal embryoid bodies, what are their role in neuron differentiation? This is matter for further studies. It is one example of what the authors says in their final statements in their original paper, when they foresee that the new technique, never applied before on embryoid body analyses, opened a whole new field of possible lines of investigation and may possible highlight hidden phenomena.

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SCIENCE HIGHLIGHTS

Figure 2. Maps showing trace element distribution in murine and human embryoid bodies. For mouse: top line, 4 days old murine embryoid body; middle line, 8 days old control embryoid body; bottom line; 8 days old neural induced embryoid body. Bright field images scale bar: 25Âľm. For human: the same, with a time period of 7 and 14 days instead of 4 and 8, as indicated. Bright field images scale bar: 50 Âľm.

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Synchrotron radiation x-ray micro�luorescence reveals polarized distribution of atomic elements during differentiation of pluripotent stem cells

Figure 3. Expression with nestin marker of neural induced human embryoid bodies. Nestin staining of H9 embryoid bodies, A) 7 days

old group; B) 14 days old control group; C and D) 14 days old neural induced group. E to H, DAPI staining; I to L, merge. The embryoid bodies depicted in this figure are corresponding examples of the total population. Scale bar 50 Âľm.

Figure 4. Left and right intensities of P, S, Cu and Zn in R1 (mouse) and H9 (human) embryoid bodies. For mouse: A) 4 days old group; B) 8 days old control groups; C) 8 days old neural induced groups. For human: the same, with time period changed to 7 and 14 days, as indicates. Left side is represented by black bars and right side by grey bars.

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15

New improvements on silica-supported ceria

Juliana M. S. Silva1, Mathias Strauss1, Camila M. Maroneze1, Ernesto R. Souza1, Yoshitaka Gushikem1, Fernando A. Sigoli1 and Italo O. Mazali1 1

Instituto de QuĂ­mica, State University of Campinas (Unicamp), Brazil

Bright field transmission tron microscopy (TEM) of (a) pure SBA-15 and (b) SBA-15/7CeO2

Facilities: 20 nm (c)

XRD-SAXS 5 nm Publication:

(d) Journal of Materials Chemistry 21, 15678 (2011)

Funding: FAPESP, CNPq, CAPES Corresponding author: Italo Odone Mazali â&#x20AC;&#x201C; mazali@iqm.unicamp.br

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New improvements on silica-supported ceria

Ceria nanosystems are known to have good catalytic properties especially interesting for greenchemistry applications such as motor vehicles exhaust gases reduction. Some recent research focus on obtaining supported ceria with stable properties suitable for practical uses. Last year Brazilian scientists had managed to build ceria nanoparticles with tunable sizes supported in a silica mesoporous matrix. Size is one of the most important parameters that in�luence nanoparticled ceria performance on reducing reactions. It was possible to control the size and the amount of ceria impregnated in the matrix, among other characteristics, just by choosing how many cycles were repeated in the synthesis procedure. The measurements allowed the authors to depict a model of the ceria distribution at the silica pores inner surfaces, and to access the variations of the parameters with the number of cycles performed.

New improvements on silicasupported ceria

In the latest decades, several research groups have been focusing their studies on ceria, or CeO2. This material – especially in nanostructured forms – has been revealing superior catalyst performances in several key chemical reactions such as steam reforming (important for petroleum derivatives production) and reduction of harmful emissions from automobile exhausts. The challenge is how to produce nanostructured ceria in a form suitable for these applications. One standard procedure is to synthesize nanoparticles coupled to a substrate called “support”, that may take different shapes, such as larger nanoparticles made of other substances or mesostructured matrices (e.g., thin  films). Last year, Brazilian scientists managed to produce nanostructured ceria dispersed in mesoporous silica in a way especially suitable for lowering vehicles pollution. This is due to fact that the resulting system has high reducing activity which is a necessary condition to catalyze the transformation of the exhaust gases in less harmful chemicals before they reach the atmosphere. Besides, the ceria particle sizes, which are known to have a strong influence on the reducing activity, are easily tunable with this technique.

decomposed the ethylhexanoate impregnated on the silica pores (by heating the system at 875 K under static air for 8 hours) in order to obtain ceria itself. The repetition of this procedure, or cycle, several times produced increasing amounts of ceria in the silica matrix with structural parameters (like partile sizes and pore diameters) depending directly on the number of cycles. Thus some of the resulting system properties could be controlled, or tuned, just by choosing the number of cycles in the synthesis process. The authors tested systems made with up to 10 cycles. All of them presented high reducing rates, important for applications in vehicles pollution reduction, as showed by measurements with temperature programed reduction with hydrogen (TPR-H2) (see Table 1, first and second columns). In reality, it was already known that nanostructured ceria reduces more easily than its bulk counterpart. This is because in ceria nanoparticles some oxygens are located in interstitial sites and are much easier to remove (except if it is calcined above 973 K). The important novelty was that the authors obtained a stable system in a suitable support with tunable properties. By its turn, the temperature at which

Table 1. Hydrogen consumption in TPR-H2 measurements per

High reduction rates

The tunability could be achieved because the synthesis method had a cyclic structure. The first cycle began with previously synthesized well-ordered hexagonal mesoporous silica structure (SBA-15). Each cycle was composed of two phases. In the first, SBA-15 was impregnated with a solution containing cerium (III) 2-ethylhexanoate. The second phase

mass of silica-supported ceria (second column) and per mass of ceria alone (third column). SBA-15/xCeO2 stands for SBA-15supported ceria obtained after x impregnation-decomposition cycles.

µmol H2 g–1 SBA–1/xCeO2

µmol H2 g–1 CeO2

SBA-15/1CeO2

201

3344

SBA-15/5CeO2

352

1324

SBA-15/10CeO2

983

2769

Sample

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the reduction began was stable, about 730 K for all samples (this value was assigned to the surface capping oxygen of CeO2). The second column of Table 1 shows the hydrogen consumption per mass of the whole system, ceria plus silica. As the number of cycles increased, the H2 consumption was higher. However, the tendency is different when the consumption is calculated per mass of ceria alone. The amount of ceria impregnated in the silica matrix and how it increased with the number of cycles were assessed with powder X-ray diffraction (XRD) together with X-ray fluorescence spectroscopy (XRF), both performed at the Brazilian Synchrotron Light Laboratory. It varyed from just 6% of the total system weight for 1 cycle to 35.5% for 10 cycles. The third column of Table 1 shows the hydrogen consumption per mass of ceria; contrary to

the previous measurements, the largest value stands for one cycle only. That might be explained from the dependence of the reducing activity with the ceria nanoparticle sizes. The ceria crystallite sizes could be calculated from the XRD measurements. The results showed that, as the number of cycles increased, the sizes decreased – which was corroborated by Raman and ultraviolet-visible spectroscopies. Well, it is known, in the scientific literature, that the smaller the ceria nanoparticles, the higher is the ceria lattice distortion – and so the higher is the density of defects in the material. Many defects in its crystalline structure, in turn, imply in ceria non-stoichiometry, that is, a Ce:O relation different from 1:2. And non-stoichiometry provides more active sites for gas-solid catalysis reactions such as those necessary

Figure 1. Bright field transmission electron microscopy (TEM) of (a) pure SBA-15 and (b) SBA-15/7CeO2; (c) dark field TEM image of SBA-15/7CeO2; and (d) HRTEM image of SBA-15/7CeO2.

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New improvements on silica-supported ceria

to reduce the harmful exhaust gases. This is why the system obtained after only one synthesis cycle, that had the smaller nanoparticles, presented the highest reduction rates per ceria mass. Other properties that vary with the number of cycles could be assessed by XRD, XRF and other experimental techniques. Thus, XRD allowed to determinate the ceria crystalline structure and how its lattice varied with the number of cycles (they varied from 5.49 angstroms for 3 cycles to 5.45 for 10 cycles). Direct images of the system were obtained with bright and dark field transmission electron microscopy (TEM) and with high resolution TEM (HRTEM) (Figure 1). They showed that the silica matrix structure was kept well-ordered after several cycles and the ceria nanoparticles were homogeneously sized and well dispersed in the matrix.

on the pore diameter was assessed by means of nitrogen adsorption-desorption tests. Gas adsorption is traditionally used to measure nano- and mesostructured surface areas; roughly (the complete process is more sophisticated), their molecules are adsorbed at the surface and so the amount of adsorbed gas indicates the surface area.

A model for ceria/SBA-15

The obtained data allowed to build a model of the positions of the ceria nanoparticles in the silica matrix and how it changes along the addition of more and more impregnation-decomposition cycles – a knowledge important as a basis for future improvements. First, it was noticed that the mesopore sizes in the silica matrix shrank as the number of cycles (and consequently the amount of impregnated ceria) increased. That apparently meant that ceria was being accumulated in the inner pore surfaces. However, pore sizes did not decrease only because of ceria adsorption: they also contracted because of the thermal treatment in the decomposition phase of each cycle. So it was necessary to assess how much of the pore size decreasing was due to ceria impregnation and how much was due to the natural pore shrinking during the 8 hours of high temperature exposition. If one could measure the distance between the pores and how it decreased with the increasing number of cycles performed, one could predict a theoretical pore shrinking due to thermal treatment only – it should just be proportional to the pore distances shrinking. Then this “predicted contraction” should be compared with the real pore shrinking measured with XRD in the LNLS (see Figure 2). The difference between the predicted and the actual pore area decreases indicated the contribution of ceria deposition to the pore size variations. The variation of the pore distances could be measured with small-angle X-ray scattering (SAXS), also made at the LNLS facilities. The actual variation

Figure 2. Representation of (A) silica matrix (without ceria)

isotropic contraction due to thermal treatment; and of (B) silica pore contraction due to both thermal treatment and ceria deposition on their inner surfaces.

Figure 3. Corroboration of the model depicted in Figure 2 (B). The measured pore area (AP(SBA-15/xCeO2)) shrinks faster than the predicted one (AP(predicted)). The auxiliar variable AT(SBA-15/xCeO2) is the area of the triangle formed by the centers of three neighbor pores.

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Figure 3 shows the differences between the predicted and the actually measured pore area variations. As the number of cycles (and the amount of deposited ceria) increases, the difference also becomes larger and larger. That confirms that the pore shrink is not only due to natural general matrix structure contraction under thermal treatment, but also because of ceria deposition at the pore inner

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surfaces â&#x20AC;&#x201C; and corroborates the model depicted in Figure 2 (B). The original work was published in the Journal of Materials Chemistry 21, 15678 (2011) by Juliana M. S. Silva, Mathias Strauss, Camila M. Maroneze, Ernesto R. Souza, Yoshitaka Gushikem, Fernando A. Sigoli and Italo O. Mazali. All figures were taken from the original article above


New data about a promising spintronic material

Siham Ouardi1, Gerhard H. Fecher1, Benjamin Balke1, Andreea Beleanu1, Xeniya Kozina1, Gregory Stryganyuk1, Claudia Felser1, Werner Klöß2, Hartmut Schrader2, Fabiano Bernardi3, Jonder Morais3, Eiji Ikenaga4, Yoshiyuki Yamashita5, Shigenori Ueda5, and Keisuke Kobayashi5 Institut für Anorganische und Analytische Chemie, Johannes Gutenbert University, Mainz, Germany 2 Fachbereich Maschinenbau und Kunstofftechnik, Hochschule Darmstadt, Darmstadt, Germany 3 Instituto de Física, Rio Grande do Sul Federal University, Porto Alegre, Brasil 4 Japan Synchrotron Radiation Research Institute, SPring-8, Japan 5 NIMS Beamline Station at Spring-8, National Institute for Materials Science, Japan 1

16 Calculated spatial distribution of the bulk, Young’s, and rigidity moduli of Co2MnGe

Facilities: XRD-XAFS1 Publication: Physical Review B 84, 155122 (2011) Funding: DfG, DfG-JST Corresponding author: Gerhard H. Fecher – fecher@uni-mainz.de

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One of the most promising materials for Spintronics is Co2MnGe. It not only keeps its magnetic properties until high temperatures (905 K) but also grows easily over semiconductor surfaces, which is a requirement for practical applications. Indeed, in 2006 and 2007 scientists managed to build a basic spintronic device, a magnetic tunnel junction, based Co2MnGe. So a comprehensive study of the properties of this material is strongly needed. Recently, German, Japanese and Brazilian researchers, have calculated and measured structural, electronic, magnetic, mechanical, vibrational and transport (electric and heat) properties. Some interesting characteristics not observed previously were found, such as an exchange splitting in the manganese energy levels measured in hard X-ray photoelectron spectroscopy experiments.

New data about a promising spintronic material

Spintronics-based technologies are recent; they are in our homes since less than 20 years and devices based on tunneling magnetoresistance, a well known spintronic phenomenon, appeared on the market in the middle of the last decade (in read-and-write heads of magnetic hard disks). Being so new, there is room for improvement that should be reached by investiganting spintronic properties of new materials. The typical systems useful for practical applications are the half-metallic ferromagnetic materials that have an energy gap for electrons with spins polarized in a certain direction, while there is no gap if they are polarized in the opposite direction. So electrons with, say, upwards spins may reach freely the conduction band of the material while ones with downwards spins may be kept imprisoned in the valence band – that is, it behaves as a metal for the former and as an isulator or a semiconductor for the latter. There are several half-metallic ferromagnetic materials, all of them composed of two or more chemical elements. Recently scientists’ attention has been driven towards the so-called Heusler magnetic compounds made of two or more non-magnetic elements. Since 1983 theoretical calculations predict that several Heusler alloys present halfmetallic ferromagnetic behavior. For practical uses in spintronics, however, there are stronger requirements. The material must have high Curie temperatures – the temperature above which it ceases to be ferromagnetic. Also, it must be easy to grow the material over a semiconductor surface – because this is how one builds most spintronic devices, such as magnetic tunnel junctions. One of the most promising candidates for spintronics is Co2MnGe, just because it is fulfilling these requirements. In 2006 and 2007, Japanese scientists managed even to build a functional

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magnetic tunnel junction with it. So the systematic and detailed study of its properties turns to be of paramount importance. A comprehensive set of data about Co2MnGe was provided in a paper published last year by a team of German, Japanese and Brazilian researchers, lead by Gerhard Fecher, from the Johannes Gutenberg University, in Mainz, Germany.

A comprehensive data set

The work presents results including theoretical calculations and experiments about structural, electronic, magnetic, mechanical, vibrational and transport properties (the last one meaning electric charge transport and heat transport). Part of the experiments were done at the Brazilian Synchrotron Light Laboratory (LNLS) facilities – specifically, normal and anomalous X-ray powder diffraction (XRD) and extended X-ray absorption fine-structure spectroscopy (EXAFS) that provided information about the material crystalline structure. The hard x-ray photoemission experiments were performed at the beamlines BL15XU and BL47XU of Spring-8 (Japan). The first step of the study consisted in the determination of the structure of the material. Preliminary results obtained with a laboratory source (Mo Kα radiation) showed that high-resolution synchrotron-based scattering experiments were necessary. The last ones allowed showing clearly that a well-ordered L21 structure was the dominant phase in the samples (typical for Heusler compounds with 2:1:1 stoichiometry). Using this determined structure, the electronic properties such as the band structure and the density of states were obtained through ab initio calculations. They indicated clearly the half-metallic character of the material, with a gap of 0.58 eV for the minority spin carriers and no gap for the majority ones, as seen in Figure 1. This figure also shows that the gap size


New data about a promising spintronic material

and position are enterely due to the cobalt atom, i.e., its high and low extremes are determined by cobalt. Interestingly enough, the groups that build a magnetic tunnel junction with Co2MnGe in 2006 and 2007 also showed that the tunneling magnetoresistance ratio, the main parameter that describe the performance of such devices, depended on the amount of cobalt in that material. Magnetic properties were also studied, both theoretically and experimentally and there was a striking coincidence between the calculated and measured ground-state magnetic moment in the primitive crystalline cell, respectively of 5 and 4.982 Bohr magnetons at a temperature of 5 K, the last value measured with a SQUID. That happened also when the site-resolved magnetic moments were determined with X-ray magnetic dichroism, XMCD. Important for the characterization of this kind of material is also the set of electronic energy levels, including the splittings due to spin-orbit interaction and exchange phenomena. A suitable experimental technique to assess these parameters is hard X-ray photoelectron spectroscopy (HAXPES). In this technique, a X-ray incident photon ejects a core or a valence electron from the material. In general, an unpaired electron will be left behind; the energy of the photoelectron is determined by the final electronic state of this remaining electron. The latter may couple in different ways to the rest of the system by means of spin-orbit and exchange effects mainly. Such interactions produce splittings in the remaining electron energy levels; information about these splittings are carried by the photoelectrons to the detectors and contain data relevant to spintronics applications. In particular, the authors found a splitting that was not observed in previous works, a Mn 3s exchange splitting of 4.68 eV (Figure 2). Another interesting finding is about the atomic ionic states, in particular manganese states. In halfmetallic compounds (as in metallic ones), some of the electrons cannot be assigned to a specific atom, but are delocalized among them. So the atoms are in fact ionized and their degree of ionization constitutes important structural information for basic science and applications. But not always the ionic states are well-defined; in the present case, the analysis of the electronic levels revealed that no definite ionic state of manganese could describe the behavior of the system.

Beyond the usually presented data

The data that follow constitutes also an interesting contribution of the authors, because in general the studies about Heusler compounds present information only about their electronic structures

Figure 1. Partial spin density of states of Co2MnGe. Black lines: majority states; red lines: minority states. Note that there are gaps in the minority but not in the majority states, revealing the half-metal character of the material. Besides, the size and position of the gap in the total density of states (fig a) is entirely due to cobalt (compare the gaps in a, b and c).

Figure 2. Hard X-ray semi-core-level photoelectron spectra (HAXPES) of Co2MnGe, taken at 300 K and excited by a photon energy of 7.9392 keV. The inset shows a magnified view of the Mn 3s state taken at two different photon energies (5.9468 and 7.9392 keV). The two peaks for each energy indicates the exchange splitting of 4.68 eV.

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and magnetic properties. There are, however, many other physical quantities that may turn to be important for later applications, namely mechanical, vibrational and transport properties. The authors presented a comprehensive study of these parameters. The mechanical quantities included those that describe the material elastic properties, mechanical stability and hardness. Figure 3 present graphs about the bulk (B), Youngâ&#x20AC;&#x2122;s (E) and rigidity (G) moduli of Co2MnGe. They reflect its cubic L21 structure; the rigidity modulus, for example, is larger along the cubic axis (along <100>-type directions).

Vibrational properties allowed extracting data about the material specific heat. By comparing calculated and measured results, it was possible to show that the specific heat is dominated by the lattice vibrations, i.e., phonons (electron and magnon contributions are responsible for deviations at higher temperatures, above 240 K). Another interesting finding was that the interatomic bondings in the material are covalent-like. This could be obtained by taking advantage of the fact that the Chin-Gilman parameter, related to the hardness properties of materials, varies systematically with the type of chemical bonding.

Figure 3. Calculated spatial distribution of the bulk (B), Youngâ&#x20AC;&#x2122;s (E), and rigidity (G) moduli of Co2MnGe.

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New data about a promising spintronic material

Transport properties included electric (resistivity) and thermal (thermal conductivity) transport. The overall low values of resistivity – 100 times smaller than those of Co2MnSi, also studied by the authors – points out the high quality of the samples. So does the low value of the residual resistivity ratio, ρ (300  K)/ρ (2K) = 1.8, that describes the small remaining constant resistivity below 50 K (Figure 4a). Thermal conductivity also presents interesting differences in its behavior below and above 50 K (Figure 4b). The original work was published in Physical Review B 84, 155122 (2011) by Siham Ouardi, Gerhard H. Fecher, Benjamin Balke, Andreea Beleanu, Xeniya Kozina, Gregory Stryganyuk, Claudia Felser, Werner Klöß, Hartmut Schrader, Fabiano Bernardi, Jonder Morais, Eiji Ikenaga, Yoshiyuki Yamashita, Shigenori Ueda, and Keisuke Kobayashi All figures were taken from the original article above.

Figure 4. Temperature dependence of the transport properties

of Co2MnGe. Shown are (a) the electrical resistivity and (b) the thermal conductivity. Note that, below 50 K, the resistivity remains practically constant.

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96 103 106 115 118 122

Accelerator Development and Operation Industrial Research Activities Beamlines

Sirius: New Brazilian Synchrotron Radiation Source Main Events

Facts and Figures


1

Accelerator Development and Operation

Brazilian Synchrotron Light Laboratory

Accelerator developments in 2011 were marked by some small scale modi�ications of the light source aiming at improving both beam characteristics and operation conditions. Efforts have been made to increase the brightness of the photon beam delivered to the beam lines by reducing the vertical coupling of the beam. Modi�ications in the accelerator systems have been implemented in order to improve the injection and ramping processes. A new dipole vacuum chamber was designed, built and installed for a new beamline that will use infrared radiation emitted at the dipoles. The emergence of the project for the new third generation light source SIRIUS brought about a whole set of studies and developments focussed on the design and speci�ication of the various systems of the new machine.

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Accelerator Development and Operation

As in the preceding years the main focus of the operation of the synchrotron light source has been on the quality of the photon beam delivered to the experimental stations. There were no major modifications planned for the magnetic lattice of the storage ring and most of the work done in 2011 concerned the continuous effort of improving the characteristics of the photon source. With the installation of new skew quadrupoles in the end of 2010 it was possible to control the coupling effect introduced by the insertion devices and reduce the vertical size of the beam delivered in the user shifts. Vertical coupling compensation was introduced in the feed-forward corrections coupled to the settings of the EPU undulator which entered in routine operation with the completion of the PGM beamline. In the operational side, an upgrade of the storage ring injection kickers improved the reliability of the energy ramps and facilitated the creation of new ramping routes. The operation of the superconducting wiggler became part of the storage ring routine procedures as the XDS beamline started to be conditioned for vacuum and commissioned with photons. The solid state RF amplifiers that were installed in the long shutdown in 2010 operated within expectations and proved to be very reliable in the RF aspects. A comprehensive reform of the air conditioning system of the storage ring building was implemented and will allow a better control of the temperature of the experimental hall. The performance of the light source suffered a setback in comparison to the exceptional results of 2010. This is basically due to the larger number of beam losses occurred along the year. Although the main individual causes of beam losses are still sags and outages in the electrical power supply of to the campus, most of the events were due to faults in the storage ring subsystems. As a result, the mean time between failures was back to its historical level, repeating the mark of 2009. In 2011 the technical teams focussed most of their attention on to the new developments required by the SIRIUS project. The activities of the engineering and accelerator groups were organized considering the studies and developments for the new source. The idea of using the current machine to test new concepts for the next light source has inspired many activities carried out along the year. Since SIRIUS has much tighter specifications than those of the current

machine, the latter will certainly benefit from any new developments that may use it for testing ground. The installation of the XDS beamline, which will use the light produced by the superconducting wiggler, started and the front end and part of the optical section of the line began to be commissioned in the middle of the year. The experimental section was installed in the beginning of 2012 and commission is under way. Two new beamlines started to be designed and parts of it built in 2011. An X-ray imaging beamline is planned to be installed in the first semester of 2012 at the 15° port of dipole 06. The second one, an infrared beamline, is planned to be installed during the long machine shutdown of 2012 at the zero degree port of dipole 03.

Accelerator Operations

The 2011 user run began in mid-January and lasted until the end of November, followed by a 7-week shutdown for upgrades and new installations in the storage ring. Two weeks of single bunch operation dedicated to time-resolved experiments were scheduled for the beginning of August. A total of 4.122 hours of beam time were delivered to users (Figure 1) and the reliability of the light source had a slight decrease to 97.6% (Figure  2). Reliability accounts for the fraction of the scheduled beam time that was effectively implemented on time. As in previous years the beam time delivered in user shifts followed the same pattern of 24 hours operation every day from Monday through Saturday morning. A change was implemented in the schedule of preventive maintenances and machine studies. Whenever possible these days were programmed in the same week in order to provide more days in sequence for machine studies. This also allowed for more comprehensive maintenance procedures and reduced the risk of affecting subsequent user shifts by machine recovery difficulties after maintenance. The installation of extra skew quadrupoles in the storage ring allowed the reduction of the vertical beam coupling and, accordingly, of the vertical size of the electron beam. As a consequence of operating with low vertical coupling the average beam lifetime dropped to about 17 hours (Figure 3) even though the impact on the average beam current in user shifts was negligible (Figure 4). A large decrease was observed in the mean time between failures which dropped from the 97 hours achieved in 2010 to about 60 hours, with a mean recovery time after failure of 1.1 hours, basically

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Figure 1. Total beam time delivered to users since 1997.

Figure 3. Average beam lifetime in user shifts since 1997.

Figure 2. Machine reliability in user shifts since 1997.

Figure 4. Average beam current in user shifts since 1997.

the same recovery time registered in 2010. Failures in the electrical power supply accounted for 30% of all beam losses during user shifts, corresponding to 36% of the total down time (DT). Almost 50% of the beam losses were caused by faults in three systems: RF (10% DT), power supplies (15% DT) and vacuum faults in the front end of the XDS beamline (15% DT). The problems with the RF system were mostly due to settings of the interlock levels and to faults in the cooling system of the new solid state amplifiers. Recurrent trips in some power supplies were related to aging of the equipments and pointed to the need for more comprehensive preventive maintenances. The cause of vacuum faults in the front end of the XDS beamline are still under investigation. Problems with the interlock settings of the line, with a vacuum pump and with ionic pump power supplies have been identified but the main problem seems to be related to the graphite filters. Along the year it was possible to recover the exceptional injection efficiency of 2009 (Figure 5). The average injection time was about 20 minutes but roughly half of the injections took less than 15 minutes

to be performed. In the second semester 70% of the injection times fell within this range. An upgrade in the storage ring pulsed magnets (components of the injection system also known as kickers) entailed both a better injection efficiency and an increase in the reliability of the energy ramping process. The incidence of beam losses during energy ramping that used to be one of the main causes of delay in the injection procedures plummeted drastically in 2011. The operation of the superconducting wiggler added an extra dead time to the ramping procedures as the field has to be ramped down to a standard set point conveniently chosen for injection. The conditioning of the XDS beamline with photon beams from the wiggler at half field started by mid-2011Â (Figure 6). Problems due to outgassing in the front end components led to many trips of the storage ring during user operation and, as mentioned above, the causes are still under investigation. The operation of the superconducting wiggler is already part of the routine operation procedures of the storage ring.

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Accelerator Development and Operation

Beam Stability

As important as machine reliability, beam stability has been one of the main concerns associated with the operation of the light source, which has already triggered several activities aiming at improving the quality of the photon beam delivered to the experimental stations. Along the preceding years several activities have been carried on to improve

Figure 5. Distribution of injection times in 2011 compared to 2010 and 2009. 70% of the injections where performed in less than 20 minutes.

the beam position measurement and orbit correction systems. Cooled masks were introduced in the vacuum chamber to prevent synchrotron light from reaching non cooled parts of the chamber as a way to reduce the thermo mechanical effects caused by the incidence of synchrotron light. After a thorough analysis all the machine beam position monitors were replaced with a new model which is less sensitive to thermal variations, mechanically decoupled from the vacuum chamber and is water cooled. These modifications were highly effective in reducing the sensitivity of the orbit correction system to thermal drifts and to mechanical deformations caused by the heating of parts of the vacuum chamber due to the incidence of synchrotron light. Currently, the activities are mainly focused on achieving better temperature control of the storage ring tunnel and of the experimental hall. In the last years inertial bocks have been installed in the experimental hall to support the critical optical instrumentation of the beamlines. These blocks are mechanically isolated from the main floor of the experimental hall and minimize the effects of mechanical noise and temperature driven movements of the floor. The effects of daily and seasonal

Figure 6. The optical section of the XDS beamline began to be commissioned in the middle of the year.

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FACILITY REPORT

temperature variations are still measurable on the electron beam orbit but have been attenuated by the changes implemented since the end of 2010. At that time, a special plastic curtain and a set of fans were installed in the storage ring tunnel to provide better temperature homogenization and stability. Since mid-2011 the air conditioning system of the storage ring building has been under a comprehensive maintenance and its control system has been upgraded for higher control flexibility. Preliminary tests performed with the system have shown that much better temperature control can be achieved in the experimental hall. Two feedback systems that will be very important for SIRIUS are being tested in the current storage ring. During the year several tests have been conducted on the transverse bunch-by-bunch feedback system. The system was installed in the storage ring in the end of 2010 and is based on a commercial digital bunch-bybunch beam position monitor. The system uses the old stripline kicker of the tune measurement system to act on individual electron bunches in order to damp transverse oscillations of the beam. Machine studies carried out at the UVX machine showed that the effectiveness of the transverse feedback depends on the damping of longitudinal oscillations of the beam. A longitudinal feedback system is being designed and the longitudinal kicker, a broadband coaxial cavity used to act on the beam, must be designed and built in 2012. The longitudinal kicker is scheduled to be installed in the UVX storage ring in the first semester of 2013. Along with the bunch-by-bunch feedback system the fast orbit correction procedure will be another key element to reach high stable beam currents in SIRIUS. The fast orbit correction system was extensively tested but still depends on the installation of new power supplies for the orbit corrector magnets. The system is based on a commercial data acquisition and control systems and is designed for fast orbit corrections at a rate of up to 3 kHz. The correction rate is currently limited by the response time of the steering magnet power supplies. One third of the new power supplies are in operation and the remaining are planned to be installed by mid-2012. Since the fast orbit system will provide better synchronization of the current adjustment of the orbit correction steering magnets it will be able to provide a smoother orbit correction than the current system.

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One year operation of the Solid State RF Ampli�iers

In late 2007, the federal funding agency FINEP approved a project to design and build two solid state amplifiers to replace the klystron tubes then driving the storage ring RF system. The motivations were twofold. First, the amplifiers would lead to smaller operation and maintenance costs. At the operation conditions of the storage ring the solid state amplifiers work have better electrical efficiency than the klystron system. In addition, due to the modularity of the amplifiers, it is much cheaper to keep spare parts for these amplifiers than keeping spare klystron tubes. Although an established and reliable technology, klystron tubes are expensive and are long lead items. Second, the amplifiers would represent a big step ahead in the effort that LNLS has been making since 1999 to master this technology, in close collaboration with Synchrotron SOLEILâ&#x20AC;&#x2122;s RF group, and which resulted in the development of three low power amplifiers that were used to drive the booster RF system. In order to replace the two klystrons of the storage ring RF system, each solid state amplifier should be able to deliver up to 50 kW of power at 476 MHz. In the period from 2008 to 2010 the two new solid state amplifiers were designed, built and thoroughly tested in the RF lab. The installation and commissioning in the storage ring took place during the long shutdown in the end of 2010. The light source operated the whole year with the new amplifiers with excellent performance in the RF aspect (Figure 7). There were some problems with the flow meters of the cooling system and with the settings of the interlock system that resulted in undesirable beam losses. However, in the RF aspect the amplifiers matched all the expectations concerning reliability and maintainability. After one year no degradation could be observed in the gain and electrical efficiency of the amplifier modules. During the whole period four amplifier modules (out of 324 in operation in both amplifiers) failed and had to be replaced. But the faults had no impact on machine operation and the replacement could be performed afterwards. The modules were all repaired in house and are now in operation in the new 2 kW amplifier that was installed in the booster RF system in the end of 2011. This new amplifier uses the same version of the amplifier modules used in the high power amplifiers, making maintenance and spare part management simpler.


Accelerator Development and Operation

Figure 7. In operation since the end of 2010, the 50 kW solid state RF amplifiers proved to be reliable and easy to maintain.

Other Developments for the Light Source

An important activity that has been under way in the last years is the upgrade of the light source control system which is also planned to be a proof of concept for the control system of SIRIUS. A new version of the low level control system, which is based on single board computers, will replace both the communication (serial and Ethernet) and the CPU cards of the current system. The system is based on Ethernet (with high level control) and RS485 (with equipment) communication protocols. In order to be mechanically adaptable to the current system a PC104 SBC is used in order to keep the same local controller crates with minimum changes in the topology of the control network. Seven SBC cards are currently in charge of most of the linac control. The communication software makes the new card completely transparent for the high level control software. Timeout problems caused by the interference of background processes in the SBC Unix-like operating system on the control system communication processes are under investigation.

In the long 2010 shutdown, the ceramic vessel chamber for a pulsed sextupole for injection tests was installed. The sextupole was built and measured throughout 2011 and was installed in the storage ring in December. Injection tests have been conducted with success and accumulation up to 250Â mA could be easily attained. The sextupole will not replace the kicker based injection system but it will allow exploratory studies for the injection system of SIRIUS. The operation voltage of the pulse forming network of the storage ring injection kickers was upgraded by 50% and the magnets are now able to produce the whole local orbit distortion needed for the injection process. The first set of power supplies for the fast orbit correction system was installed in the storage ring. These power supplies embed many innovations that are going to be developed and implemented in the power supplies for SIRIUS. The power system comprises an AC/DC power module that feeds up to four DC/DC power supplies. These DC/DC modules can be independent or may be combined to provide a higher output current. The device has digital setting, no forced cooling and meets the requirements of the fast orbit feedback system.

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FACILITY REPORT

During the long shutdown at the end of 2011 a new dipole vacuum chamber was installed in the storage ring. The new chamber has a zero degree photon beam port that will be used for a new infrared beamline that is under construction. The chamber incorporates some concepts that are being tested for the vacuum chambers of SIRIUS such as using embedded pumping elements for higher pumping efficiency.

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Although the activities connected to the SIRIUS project have been quickly scaling up the attention given to the UVX light source has not dwindled. Improving machine reliability and beam stability, as well as working out new research possibilities for the light source, are permanent goals that have been diligently pursued by the LNLS team. The technological advances necessary for SIRIUS are leading to new developments and learning that will be beneficial to the UVX source.


Industrial Research Activities

2

Sample-holder used for remote controlled SAXS experiments.

The LNLS has been a partner with industries in the development of various projects. The principal projects in 2011 were the Premium Screens Quali�ication Project, in partnership with Statoil Brazil S/A, the Labweb Project which allows remote access to the beamlines, �inanced by CENPES/ PETROBRAS, and in partnership with Braskem for the analyses of the microstructure of ultra-high module polyethlene �ibers to be used on marine petroleum exploration platforms.

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FACILITY REPORT

Technological Partnerships Statoil

The Premium Screens Qualification project in Brazil is carried out in partnership with the Statoil Brasil S/A. It has a team specifically dedicated to the project, as well as various professionals from areas of the CNPEM/LNLS. In 2011, numerical simulations, purchasing of materials for the prototypes and equipment were concluded. In total 24 prototypes of Premium screens in full scale were produced for testing traction, torsion, folding, crushing and tearing of the protective frame, all these tests were carried out at IPT in Sao Paulo. Also corrosion tests were carried out at LAMEF/UFRS and sand retention at LABFRAC/UNICAMP. Lastly, corrosion and erosion tests were carried out in a loop specially designed and constructed for this purpose at LABEDIN/FEM/UNICAMP. All the tests produced very encouraging results within the specification provided by Premium screens. 2011 was the year for the construction of prototypes (Figure 1), equipment and the carrying out of tests. All prototypes were designed and constructed conforming to the schedule initially proposed. In addition to the benefits brought to the Materials Group in terms of direct investment for the laboratory

with the purchase of equipment for the preparation and characterization of materials, the project also guaranteed the acquisition of numerical simulation software ANSYSŠ (including 6 academic licenses for the general use of CNPEM)

Diffusion Welding Technology The diffusion welding process depends on important parameters such as, controlled atmosphere, constant charge and elevated temperature to guarantee the joining of the filter elements made of stainless steel 316L, of which the Premium screen is composed. The Figure 2 shows the microstructural characterization of the filter element welded by the diffusion process, in which it is possible to observe the interface between the metallic fibers which compose the element. The sample was polished with an electrolytic solution and reveals grain contour and precipitates typical of an austenitic structure. The results presented show the filter element integrity and consequently the capacity for the retention of solids after the tests were finalized. In conclusion, the diffusion welding process for application in the filter element of Premium Screen was developed with success, even for parameters non optimized.

Figure 1. Premium Screens: partnership with the Statoil Brazil to produce prototypes.

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Industrial Research Activities

Figure 2. Optical microscopy (a) Filter element welded by diffusion and (b) increased detail of material microstructure (400x).

Labweb This project, financed by CENPES/PETROBRAS, has as main objective to upgrade the beamlines, or even similar scientific facilities, to allow their remote operation from distant research centers. In other words, the project allows a researcher to operate and carry out experiments on the LNLS beamlines from a web browser in any part of the country, or even the world. The project was divided in two parts to be carried out in parallel. One is the restructure and replacement of the in-house proprietary control systems (both hardware and software) to systems which work with communication technologies that have already a widespread in other synchrotrons. The chosen solution was the open source EPICS platform associated to the PXI (PCI extensions for Instrumentation) modular electronic instrumentation platform. PXI is based on industry-standard computer buses and permits flexibility in building equipment. Besides the versatility and practicality of the equipment, the development of a hybrid concept of data acquisition in real time along with the standard EPICS channel-access protocol has been developed in partnership with National Instruments of Brazil. More details are given in the beam line development section of this report.

The development of the remote operation interface is being developed in partnership with the Canadian Light Source. Using a prototype system developed first by LNLS and the Venturus Innovation Center the first operation and remote data acquisition on the SAXS-1 and XRD-1 lines were carried in the middle of 2010. After that the software developed on the prototypes were incorporated into the The Canadian system called Science Studio, based on web applications written in JAVA, which allows the executing and operating in practically any computer web browser.

Braskem One of the new target markets of Braskem, the largest producer of thermoplastic resins in the Americas, is the high performance fibers. This is extremely competitive and requires a deep understanding of the fiber microstructure using synchrotron techniques. The project began in December 2011 and involves theoretical calculations and experimental assessment of the microstructure of high performance fibers using synchrotron techniques. The main objective is to improve mechanical properties of Ultra High Molecular Weight Polyethylene in a way that can be utilized for anchoring cables used on marine petroleum exploration platforms.

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3

Beamlines

PGM: a beamline based on a APPLE II undulator.

In preparation for the upcoming new synchrotron beamlines on Sirius, the UVX beamlines are still going through upgrades, either introducing new experimental techniques or new experimental stations that will be later transported on the new synchrotron. The highlights of these upgrades are described in this section.

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Beamlines

Presently, there are sixteen beamlines at the UVX storage ring of LNLS in operation, most of them (thirteen) based on bending magnets and only three on insertion devices: a PGM using a APPLE II undulator, an X-ray diffraction and Spectroscopy beamline based on a 4 Tesla superconducting wiggler and a protein crystallography beamline based on a hybrid 2T wiggler. The beamlines are organized in five groups, X-ray Scattering and Macromolecular Crystallography, X-ray Absorption and Fluorescence, X-ray Diffraction, Ultraviolet and Soft-X-ray Spectroscopies and the new Imaging group, introduced in 2011. This group has an x-ray tomography beamline, which is under commissioning. In general, the recently improved budgetary situation, thanks to federal and private investments, boosted the development of most of the beamlines. The new instrumental developments are nearly ready and their implementations will be available in 2013.

Beamline Control

One example of genera l inf rast r uc ture development resulting from these new investments is the refurbishing of the control system in all the beamlines financed by PETROBRAS through the labweb project. This development aimed at remote controlling the beamlines using the widespread EPICS (Experimental Physics and Industrial Control System) control platform, together with the commercial, off the shell, PXI/Labview Real Time hardware/software system, widely available in Brazil. The Hyppie system, developed in collaboration by the LNLS software group and National Instruments Brazil, makes a bridge between EPICS records in a Linux server and the corresponding devices controlled by Labview RT, in the PXI chassis. Both operational systems run in parallel over a virtualization software, Hypervisor (from NI and Intel), and exchange data with high throughput in real time through a piece of shared memory provided by Hypervisor. This memory is allocated by Hyppie as a map to deal with each piece of hardware, through commands, parameters and readout. EPICS IOCs (input-output channels) running in the Linux side refer to the shared memory instead of any direct I/O access. This new system has the advantage to use a friendly real time environment, like Labview RT, to deal with the low level hardware control, leaving only the network broadcasting and distribution system to EPICS. Several different peripheral equipments have been integrated to EPICS rather easily thanks to the new system.

With the EPICS system creating a hardware virtualization it is now possible to access experiments remotely, even through a web interface, which is the final objective of this project. The browser access software part of this project is being developed in collaboration with the Canadian Light Source, within their remote access platform, Science Studio. Along this year, 4 beamlines received the new hardware control system and a web interface was created for the experiments at LNLS using Science Studio. This will continue on the other 14 beamlines along the next years.

Sample Stages

The general infrastructure for sample stages and gases for in-situ experiments in the beamlines also received some upgrades, like the development of a high pressure gas injection system at low temperatures, used at the diffraction beamlines, a new mass spectrometer and gas detectors, to supply the ever increasing demand for synchrotron experiments with specialized sample environments, and a new reactor for liquid samples that can reach 500 °C, with an adjustable optical path has also been developed, which is mostly used at the diffraction beamlines. There is now a dedicated area in the experimental hall with a similar infrastructure of gases and liquids found on the beamlines, which allows a pre-treatment of samples, saving beam time of the beamlines. Also, the sample preparation lab is now connected to the main experimental floor, facilitating the preparation and transit of samples to the beamlines

The new imaging beamlines

The two new bending magnet beamlines recently created are dedicated to imaging in the two extremes of the radiation spectrum produced by the UVX ring bending magnets, one in the infrared and the other in the X-rays. The x-ray tomography beamline (IMX, Figure 1 and Figure 2) is currently being commissioned, and its first results are very encouraging. The beamline is currently working with 30% band pass pink beam around 14 keV, but in the near future will also be able to work with 2% bandpass multilayer around 14 keV for use with a Talbot interferometry setup (already assembled but waiting for the multilayers). The current resolution of the microscope is still in the range of 10 µm, but with a new camera that is being constructed we expect to reach sub µm resolution with very fast acquisition times, thanks to the high flux provided by

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FACILITY REPORT

Figure 1. Motorized detector and sample stages at IMX.

the synchrotron pink beam. The entire control system for this beamline was based on the Hyppie platform, allowing very low dead times. The infrared beamline will also be a novelty for the LNLS community, and will provide a one- of-a-kind experiment with synchrotron infrared. A new optical concept created in collaboration with Paul Dumas and Thierry Moreno from Soleil is being put to work to provide a very collimated (1.1 mrad × 0.6 mrad divergence) IR beam. This beam will be coupled to a commercial scanning near field optical microscope (SNOM) adapted for infrared, which is able to produce better than 100 nm lateral resolution on IR imaging (Figure 3). The SNOM is currently working with a He-Ne laser (633 nm) for commissioning and will be transferred to the beamline in the first semester of 2013. An image of gold nano-doughnuts obtained with the SNOM setup is shown in Figure 4

X-ray Absorption and Fluorescence

In terms of new optics, the main addition to this group of 4 BM beamlines along the last year was a KB mirror for micro-fluorescence that is under installation at the XRF beamline. Along with the new

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Figure 2. Detail of the rotation stage in commissioning with a test sample.

micro focusing system, a completely new rotation/ translation sample stage has been developed for the micro-fluorescence experiments. The KB mirror system has been built by the ESRF and will allow a 9 × 18 µm2 focusing at sample position, with a working distance of about 0.1 m. This new experimental setup (Figure 5) will be available in the first semester of 2013. In 2011 there were major improvements in the high pressure techniques at the LNLS, and for the future synchrotron radiation source, Sirius. With the current setup (see Figure 6) it is possible to carry out experiments at LNLS with up to a maximum of 35 GPa (350 thousand atmospheres). With the improvements to the experimental techniques, it will soon be possible to achieve pressures of up to 80 GPa. On Sirius, beam sizes as small as 30 nm will be achieved, which will allow carrying out experiments at pressures higher than 370 GPa – the pressure at the center of the earth. Some new high pressure instrumentations have been put together to improve these experiments at LNLS and to be prepared for Sirius. From these we can cite: • A new Micro Electrical Discharge Machine, capable of drilling holes of diameter down to


Beamlines

Figure 3. Layout of the IR beamline with the SNOM endstation.

Brazilian Synchrotron Light Laboratory | 109


FACILITY REPORT

Figure 4. Topographic and SNOM data of a gold nano-doughnuts.

Figure 5. The design of the new micro-fluorescence setup based on KB mirrors that will be implemented in the end of 2012.

30 microns centered at pre-indented gaskets is now used. • A new ruby system was assembled, very light for easy assembly at any setup at the beamline, more sensitive, with a higher precision measuring the ruby fluorescence line, and also have an image system, that allow seeing the laser focusing at the gasket hole. • The pressure can be controlled by a membrane system, with the main advantage of allowing low temperatures experiments with a new cryostat chamber, without opening it.

110 | ACTIVITY REPORT 2011

X-ray Diffraction

This group has four beamlines, 3 based on BM: D10A:XRD2, D10B:XPD and D12A:XRD1 and a 4T superconducting wiggler beamline that was designed to be partially dedicated to x-ray absorption and to diffraction. This is the first beamline at LNLS able to reach energies as high as 30 keV with a good flux, thanks to the 4T wiggler. The opening of this beamline was unfortunately delayed for more than a year after its construction, due to the delayed delivery of a mirror and after problems in the front-end vacuum.


Beamlines

Figure 6. The high pressure setup in use at the Dispersive X-Ray absorption beamline.

Now the beamline is operational and the first results are very encouraging. Figure 7 shows a PDF result of and a x-ray absorption spectrum up to energies around 30keV, these experiments were performed at the highest energies ever achieved at LNLS. Along 2011 the XRD1 beamline optics went through a refurbishing, increasing the energy stability and, shape and position stability of the x-ray beam. The beamline is now ready to receive a new heavyduty diffractometer for powder diffraction from Newport. The beamline will also be fully automated with a robot for sample exchange that is currently being constructed. We expect to have a state of the art powder diffraction station in the first semester 2013, which will later be transferred completely to Sirius. Another highlight in the XRD1 beamline was the commissioning of the recently developed X-ray Scattering and Thermo-Mechanical Simulation

(XTMS) experimental station (Figure 8). The setup was commissioned by the Brazilian Nanotechnology National Laboratory (LNNano) team with the collaboration of LNLS. The simulator is a custom built Gleebleâ&#x201E;˘ system, which allows submitting materials of interest to a wide range of thermo-mechanical conditions with high accuracy and reproducibility. Linear or area X-ray detectors are mounted in a highresolution goniometer. Accessory instrumentation includes optical elements for incident beam control, automated sample alignment, liquid nitrogen cooling system and a non-contact laser dilatometer.

X-ray Scattering and Macromolecular Crystallography

Following the complete refurbishing of one of the two small-angle scattering beamlines (SAXS1), new experiments with time resolution are being

Brazilian Synchrotron Light Laboratory | 111


FACILITY REPORT

implemented, like stopped-flow SAXS and RheoSAXS. A new sample stage has been created to allow these heavy equipments that can hold up to 100 kg. The Rheo-SAXS setup (Figure 9, left) commissioning is ongoing and tests with partially transparent Couette flow cell have been successfully done. The stopped flow system (Figure 9, right), which will allow the study the dynamics of nanostructure formation by mixture of liquids, can do controlled mixtures of 1:1 to 1:100 proportions, with a dead time of order of 1 ms. Both these setups will soon be available to external users. Another implementation of sample stage has been done that allows a quick exchange between

liquid and solid sample stages. The liquid sample stage typically used at our SAXS beamlines is able to produce minimal background scattering. However since it works under vacuum, it has the disadvantage of been a very slow throughput when dealing with solid and gel samples. This problem has been solved with a new sample stage (Figure 10) that allows the user to quickly exchange between liquid and solid sample stages with a minimal background scattering. This has an enormous impact on the usability of the beamlines. The IRELEC robot for sample change in the Macromolecular crystallography beamline MX2 is now fully operational, providing the users with state of the art instrument for protein crystallography. We expect that the industrial usage of this beamline will also increase now thanks to the increased agility.

Ultraviolet and Soft-X-ray Spectroscopies

Figure 7. Result of na x-ray absorption spectrum up to energies around 30keV.

This group is responsible for four beamlines, three in the UV range (the U11A: PGM, D05A:TGM and D08A:SGM) and one in the soft-X-ray range (D04A:SXS). During 2011 PGM received its first 2 rounds of users and its performance has reached the design goals, as published in the 2012 SRI conference, in Lyon. Each of its two branch lines can be equipped

Figure 8. View of the X-Ray Scattering and Thermo-Mechanical Simulation setup.

112 | ACTIVITY REPORT 2011


Beamlines

with a variety of experimental chambers, which are shared within the LNLS ultra-violet and soft X-rays beam lines. In particular, the following end stations are available: • 1.5 T electromagnet, UHV compatible, associated with a basic preparation chamber (sputtering, annealing, MBE evaporator and LEED). This

chamber is mostly used for X-ray magnetic circular dichroism (XMCD) of in-situ prepared samples; • 6.5 T superconducting magnet for XMCD of exsitu prepared samples; • Scienta R4000 electron analyzer for XPS on gas or liquid phase samples under near ambient pressure conditions;

Figure 9. (left) The rheo-SAXS setup for studying in-situ microstructure of soft materials under deformations. (right) The new stop-flow system being tested on time-resolved experiments for observing the formation of nano-structures from fast liquid mixtures.

Figure 10. The sample stage to use solid samples with the same liquid sample setup under vacuum, which will allow much faster setup changes during SAXS experiments.

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FACILITY REPORT

• Specs Phoibos 150 electron analyzer for XPS on solids; • Four circle diffractometer for soft X-ray magnetic scattering or reflectivity • multicoincidence time of flight mass spectrometer for atomic or molecular studies. The resolution power and flux compare well with the ray tracing simulations (Figure 11) and are within a factor 2, excepted between 200 and 300 eV: in this region, we use the second harmonic (red dots) which has a lower intensity and there is a small carbon contamination. This is due to the fact that we can’t decrease the undulator gap below 22 mm, creating a “hole” between the first and third harmonic. Several user projects on magnetism, surface science and atomic and molecular physics have been performed at this beamline along 2011 and the first publications start to appear. A major investment is being now done on the end stations, and a new Angle Resolved Photoemission (ARPES) system, with a Photo Electron Emission Microscope (PEEM) has been purchased.

114 | ACTIVITY REPORT 2011

This system should be installed in the end of 2013 and later transferred to Sirius. A complete refurbishing of the soft x-ray reflectivity chamber has also started with the addition of a soft-x-ray CCD (a PI-MTE2048B from Princeton Instruments) has been purchased and new motorized stages are being planned.

Figure 11. Flux and resolution power for a current of 200mA, an exit slit of 200µm and c=2.25. The ray tracing simulations (in gray) and the measured values (different color for each harmonic) are in good agreement, within a factor two, excepted in the region 200300eV in which we have to use the much weaker second harmonic.


Sirius: New Brazilian Synchrotron Radiation Source

4

Sirius: a new Brazilian synchrotron radiation source

LNLS has been working on the design of a new synchrotron radiation source (Sirius) since the beginning of 2009, with a brilliance comparable to those in planning or construction phases around the world. The design also includes some innovations in order to reduce investment and operational costs. The planned result is considered to be an important tool for the development of the country.

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FACILITY REPORT

Technical characteristics

One of the characteristics of the proposed design is the use of permanent magnets for the production of the magnetic dipole fields. This eliminates the use of large power supplies and reduces the power consumption by a significant amount if compared

Comparison of brightness of Sirius with that of the existing synchrotron radiation source (UVX) in operation at LNLS for dipoles, superconducting wiggler (WSC) and an undulators with 20 mm period (U20).

to the use of conventional electromagnetic dipoles. Also, since all the power used in electromagnets is dissipated as heat, the use of permanent magnets produces no load on the cooling systems of the facility, reducing even more the investment and operational costs. A second characteristic of this design is the use of very weak magnetic fields in most of the dipoles (94% of the total length of dipoles is at 0.5 Tesla). The remaining 6% present a high field (2 Tesla) in order to produce useful synchrotron light only where necessary. Since the unused synchrotron radiation only burdens the vacuum and radiofrequency systems, this approach produces additional savings in investments and operational costs. Besides these innovations, Sirius is designed to be a state of the art synchrotron radiation source. Some important design parameters of the Sirius are presented in the following table and are compared to those of facilities in construction or operation around the world as well as to the existing source at LNLS.

Energy (GeV)

1,37

3,0

2,75

3,0

3,5

3,0

Average diameter (m)

30

153

113

179

137

252

Brightness from dipoles @ 10 keV*

1

5600

1560

3600

2200

370

Brightness from dipoles @ 50 keV*

1

25.109

1,9.109

4,4.109

5,8.109

2700[4]

Emittance (irrespective of insertion devices) [nm.rad]

100

1,8

3,7

2,7

3,9

2,1

Notes: [1] in operation; [2] in design; [3] in construction; [4] the design does not envisage dipole beamlines. *related to the LNLS source.

Comparison of Sirius with todays LNLS source and most facilities in construction or operation.

116 | ACTIVITY REPORT 2011


Sirius: New Brazilian Synchrotron Radiation Source

CNPEM campus

Cross-section of the Sirius building.

Innovative design

Intense light only for the beamlines Strong magnetic field only where necessary Low light intensity was not necessary

Permanent magnet dipoles Lower investments

• In power supplies • Less power for cooling systems

Lower operational costs

• 2.5 GWh/year savings in Power supplies • Lower load on cooling system (0,5 GW.h/year) • Higher reliability (less critical components)

Strong magnetic �ield only where necessary Lower investments

• In high power RF equipment • In vacuum equipment (less heating and photo-desorption from unused synchrotron radiation)

Lower operational costs

• 4 GW.h/year savings in RF power generation • Lower load on cooling system (0.8 GW.h/year)

Use of solid state RF power ampli�iers Lower investments

• 3 GW.h/year savings in RF power generation

Annual savings of 11 GWh

Brazilian Synchrotron Light Laboratory | 117


5

Main Events

Mr. Aloizio Mercadante, Brazil´s Minister of Science, Technology and Innovation, was introduced to the prototypes of magnets that will be used in the new synchrotron light source

In 2011, LNLS signed a collaboration agreement with Deutshche Elektronen-Synchrotron (DESY), the European XFEL GmbH; hosted the São Paulo Advanced School: New Developments in the �ield of Synchrotron Radiation and the 21st International Congress on X-ray Optics and Microanalysis (ICXOM21); was visited by the Chief Scienti�ic Adviser to the UK Government, Sir John Beddington, and was honored with the SciVal Brazil 2011 Award which highlights the scienti�ic institutions that contribute to the development of the country, these are among many other important events that took place this year.

118 | ACTIVITY REPORT 2011


Main Events

International Partnership

Brazil and Germany signed a collaboration agreement in May for research in the area of synchrotron light. The partnership involves Deutshche Elektronen-Synchrotron (DESY), the European XFEL GmbH and LNLS, for collaboration in the areas of physics accelerators, the use of Synchrotron Radiation, Free Electron Lasers, as well as the development of optical components, new technologies and detectors. The agreement was signed within the framework of the Brazil-German Science Year 2010/2011 and was signed by the German president Christian Wuff and by the Brazilian president Dilma Roussef. At the beginning of the year, Brazil had already signed a memorandum of understanding with Argentina for the development of projects related to Sirius, the new Brazilian Synchrotron Light Source. The memorandum signed by the Ministers of Science and Technology for Brazil and Argentina, Aloizio Mercadante and Lino Baraño, respectively, foreseeing the exchange of researchers and the constitution of a workgroup to coordinate and evaluate the progress of research.

São Paulo Advanced School

The LNLS hosted the São Paulo Advanced School (ESPCA, the acronym in Portuguese): New

Developments in the field of Synchrotron Radiation. Sponsored by FAPESP, ESPCA aims to promote interaction between researchers from Brazil and other countries. The school brought together 64 Brazilian and foreign researchers and two Nobel Prize winners: Ada Yonath (Chemistry, 2009) and Albert Fert (Physics, 2007).

Chief Scienti�ic Adviser to the UK Government visited LNLS

The Chief Scientific Adviser to the UK Government, Sir John Beddington, visited the LNLS on May 12, 2011. Sir Beddington was shown the project of the new Brazilian synchrotron light source and indicated the possibility of partnerships with British Petroleum (BP) and other companies in the oil and gas sector.

Award SciVal Brazil 2011

The LNLS was honored with the SciVal Brazil 2011Award which highlights the scientific institutions that contribute to the development of the country. The Award is conferred by Elsevier Publishing with support from the Coordination for the Improvement of Graduated Personnel of thel Ministry of Education (CAPES / MEC ). The winners were chosen by their

Ada Yonath, Chemistry Nobel Prize 2003, at São Paulo Advanced School.

Brazilian Synchrotron Light Laboratory | 119


FACILITY REPORT

The Chief Scientific Adviser to the UK Government, Sir John Beddington, at LNLS.

scientific production, collaboration with Brazilian and foreign institutions and citations for papers in the period 2006-2010. The LNLS recorded the highest percentage of articles published in collaboration with other Brazilian research institutions.

Minister Mercadante visits LNLS

On May 11th, 2011, Mr. Aloizio Mercadante, Brazil´s Minister of Science, Technology and Innovation, visited CNPEM where he was shown the prototypes of magnets that will be used in the new synchrotron light source. He also announced that the Brazilian Nanotechnology l Laboratory (LNNano) will host the Binational Nanotechnology Center that Brazil will create in partnership with China.

ICXOM21 at LNLS

LNLS hosted the 21st International Congress on X-ray Optics and Microanalysis (ICXOM21) from 5 to 8 September 2011. The ICXOM21 was dedicated to bring together scientists and technologists involved in fundamental and applied research in the field of micro (nano) analysis by means of X-ray beams, with an emphasis on synchrotron sources, electrons and other energetic particle, or active in methodology

120 | ACTIVITY REPORT 2011

and instrument developments. The first ICXOM was held in Cambridge, United Kingdom, in 1956 and the latest four editions in the took place in Germany (Karlsruhe-2009), Japan (Kyoto-2007), Italy (Frascati-2005) and France (Chamonix-2003). For the first time a congress will be held in a LatinAmerican country.

LNLS Scienti�ic Committee

The LNLS Scientific Committee was in the campus in the period of February 27th until March 02nd. The Scientific Committee meetings are held every two years. More information about the Scientific Committe Report 2011 can be checked on the website: http://www.lnls.br/for-users/scientific-comitee/.

21st LNLS Annual Users Meeting

The 21st edition of the LNLS Annual Users Meeting (AUM), held on February 22 and 23, 2011, brought together 300 researchers from Brazil and abroad, who presented the results of their scientific research using synchrotron radiation (Figure 1). In addition to thematic sessions, plenary meetings were held with Gang Oleg, from Brookhaven National


Main Events

Laboratory; Peter Cherepanov, from Imperial College of London; Adam Hitchicock, from McMaster University; and Vitali Prakapenka, from Argonne National Laboratory. The meeting’s agenda included three workshops: The Applications of Neutron Beams, a Biomolecular Crystallography Course and a Microfluidics Workshop.

New board at CNPEM

On August 19th the board of the Brazilian Association of Synchrotron Light Laboratory (ABTLuS), elected its new president, Pedro Wongtschowski, and the new director general of the Brazilian Center for Research in Energy and Materials (CNPEM), Carlos Aragão de Carvalho Filho.

The 21th RAU edition: 300 researchers from Brazil and abroad. Crédito Celso Congilio.

Brazilian Synchrotron Light Laboratory | 121


6

Facts and Figures

Brazilian Synchrotron Light Laboratory, the only one in Latina America

In 2011, users submitted 443 research proposals and used the 14 synchrotron beamlines. Of this set of proposals, 80% were submitted by Brazilian researchers and 20% by foreign users, mainly from Argentina. Another 140 research proposals were developed at the facilities of the Cesar Lattes Center for Nanoscience and Nanotechnology (C2Nano) from January to July 2011. The current source operated from January to November 2011, 24 hours a day, Monday through Saturday morning, and the project of the second Brazilian synchrotron light source made considerable progress in 2011.

122 | ACTIVITY REPORT 2011


Facts and Figures

The Brazilian Association for Synchrotron Light Technology (ABTLuS) is a private nonprofit center that operates the LNLS through a management agreement signed with Brazilâ&#x20AC;&#x2122;s Ministry of Science,Technology and Innovation (MCTI), in line with Executive Order 2405 of November 26, 1997. In 2011, ABTLuS comprised the Brazilian Synchrotron Light Laboratory (LNLS), the National Biosciences Laboratory (LNBio), the Brazilian Bioethanol Science and Technology Laboratory (CTBE) and the Brazilian Nanotechnology National Laboratory (LNNano), installed in july 2011. LNNano now includes the Electron Microscopy Laboratory, the Microfabrication Laboratory and the Scanning Probe Microscopy Laboratory, installed at Cesar Lattes Center for Nanoscience and Nanotechnology (C2Nano), which was previously managed by LNLS. The project of the second Brazilian synchrotron light source made considerable progress in 2011. Most of the accelerator and engineering team efforts involving the Sirius Project focused on the refinement of this lattice design and on magnet prototyping. Also, in preparation for the challenges of building components

for Sirius, the physical infrastructure underwent a major upgrade. The current source operated from January to November 2011, 24 hours a day, Monday through Saturday morning. Weeks with holidays were reserved for maintenance and machine studies wherever possible. During 11 months of operation, users and researchers used 4,123 hours of beam to conduct experiments on the 14 available beamlines. The source reliability index reached 97.6%, a percentage similar to that of previous years. In 2011, users submitted 443 research proposals and used the 14 synchrotron beamlines. Of this set of proposals, 80% were submitted by Brazilian researchers and 20 by foreign users, mainly from Argentina (74). About 140 research proposals were developed at the facilities of the Cesar Lattes Center for Nanoscience and Nanotechnology (C2Nano) from January to July 2011. With regard to scientific production, 337 scientific papers were published in indexed journals, 38 of them with an impact factor higher than 5.

Brazilian Synchrotron Light Laboratory | 123


FACILITY REPORT

Proposals

2011

Submitted

Accepted

Executed

Canceled

MX1/MX2

77

65

56

13

XAFS1XAFS2

114

71

69

1

XRF

43

32

29

3

DXAS

41

29

31

0

SXS

37

22

22

0

TGM

27

21

19

2

SGM

38

22

9

13

XRD1

41

30

19

11

XRD2

47

31

32

0

XPD

83

42

43

0

SAXS1/2

168

114

114

0

TOTAL

716

479

443

43

2011

MX1/ MX2

XRF

DXAS

XAFS1/ XAFS2

TGM

Requested

166

114

147

248

167

151

252

146

223

394

357

2365

Accepted

122

104

119

211

111

106

140

91

119

132

174

1429

2011

MX1/ MX2

DXAS XAFS2 TGM

SXS

Accepted

XRF

XAFS1/

SXS SGM XRD1 XRD2 XPD

SGM XRD1 XRD2

XPD

SAXS1/ TOTAL SAXS2

SAXS1/ TOTAL SAXS2

122

104

119

211

111

106

140

91

119

132

174

1429

Completed 107

102

120

226

117

102

96

93

119

128

176

1386

124 | ACTIVITY REPORT 2011


Facts and Figures

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

S達o Paulo State

65%

62%

60%

62%

57%

51%

51%

44%

46%

39%

42%

40%

Other States

20%

23%

25%

23%

28%

32%

33%

39%

36%

42%

40%

40%

Other Countries

15%

15%

15%

15%

15%

17%

16%

17%

18%

19%

18%

20%

Brazilian Synchrotron Light Laboratory | 125


FACILITY REPORT

126 | ACTIVITY REPORT 2011


Small-Angle X-ray Scattering

Macromolecular Crystallography

Soft X-ray Spectroscopy

X-ray Absorption Fine Structure

Toroidal Grating Monochromator

Dispersive X-ray Absorption Spectroscopy

Spherical Grating Monochromator

X-ray Absorption Fine Structure

Superconducting Wiggler BeamLine

X-ray Fluorescence

X-ray Diffraction

X-ray Powder Diffraction

High Resolution VUV Spectroscopy

X-ray Diffraction

X-ray Image

D01B

D02A

D03B

D04A

D04B

D05A

D06A

D08A

D08B

W09B

D09B

D10A

D10B

U11A

D12A

D06B

Infrared

Small-Angle X-ray Scattering

W01B

D03A

Name

Macromolecular Crystallography

Source

IR1

IMX1

XRD1

PGM

XPD

XRD2

XRF

XDS

XAFS2

SGM

DXAS

TGM

XAFS1

SXS

MX1

SAXS2

SAXS1

MX2

Acronym

FTIR interferometer

White beam and Double Multilayers 6-14 keV

Focusing Double crystal 5-15 keV

Planar Grating 100-1200 eV

Focusing Double crystal 5-15 keV

Focusing Double crystal 5-15 keV

White beam or double crystal 5-25 keV

Doble Cystal 5-30 KeV

Focusing Double crystal 4-17 keV

Spherical Grating 100-1200 eV

One single-bent crystal 5-12 keV

Toroidal Grating 12-300 eV

Channel cut 3-25 keV

Double crystal 1500-5500 eV

One single-bent crystal 6-12 keV

One single-bent crystal 6-12 keV

One single-bent crystal 6-12 keV

Focusing Double crystal 5-15 keV

Monochromator

Applications

Reference

Near field scanning Infrared Microscopy

Absorption ad phase contrast tomography

Single crystal diffraction, Multiple Beam Diffraction

Surface and Interfaces. Atomic and Molecular Physics, X-ray Magnetic Dichroism

Power Diffraction Studies in Materials Science

Magnetic Scattering, Grazing Incidence, Nanostructures

Environment and Geochemistry, Biophysics and Agriculture

Materials Science

Materials Science, thin films and diluted systems

Surface and Interfaces. Atomic and Molecular Physics

Materials Science, In-situ Studies, Magnetic Dichroism

Surface, Atomic and Molecular Physics; Time-of-Flight

Materials Science, thin films and diluted systems

Photoabsorption and photoemission spectroscopy

Structural Molecular Biology

Glasses and Nanocrystals, Polymers and Molecular Biology

Glasses and Nanocrystals, Polymers and Molecular Biology

Structural Molecular Biology using MAD technique

A

A

A

A

A

Detectors

Sample enviroment

Rheometer

Status

Project

Construction

Operational

Construction

Operational

Operational

Operational

Comissioning

Operational

Operational

Operational

Operational

Operational

Operational

Operational

Operational

Operational

Operational

Facts and Figures

Brazilian Synchrotron Light Laboratory | 127


ARTICLES PUBLISHED IN INDEXED JOURNALS

Articles published in indexed journals

1. Internal research team

1 - Human stanniocalcin-1 interacts with nuclear and cytoplasmic proteins and acts as a SUMO E3 ligase (3364) Santos, M. T., Trindade, D. M., Gonçalves, K. de A., Bressan, G. C., Anastassopoulos, F., Yunes, J. A., Kobarg, J.

Molecular BioSystems, 2011, v. 7, n. 1, p. 180- 193 Fator de Impacto em 2010: 3,825

2 - Functional and biophysical characterization of a hyperthermostable GH51 alpha-L-arabinofuranosidase from Thermotoga petrophila (3593) dos Santos, C. R., Squina, F. M., Meza, A. N., Oldiges, D. P., Paes Leme, A. F., Ruller, R., Mort, A. J., Prade, R. A., Murakami, M. T.

7 - Human Nek6 is a monomeric mostly globular kinase with as unfolded short N-terminal domain (3637)

Meirelles, G. V., Silva, J. C., Mendonça, I. A., Ramos, C. H. I., Torriani, I., Kobarg, J.

BMC Structural Biology, 2011, v. 11, 12-1-13 - Fator de Impacto em 2010: 2,258 8 - Silica-maltose composites: obtaining drug carrier systems through tailored ultrastructural nanoparticles (3673) Leirose, G. D. S., Cardoso, M. B.

Journal of Pharmaceutical Sciences, 2011, v. 100, n. 7, p. 2826-2834 - Fator de Impacto em 2010: 3,031

Pérez, R. D., Sánchez, H. J., Rubio, M., Pérez, C. A.

9 - Molecular cloning, overexpression, puri�ication, crystallization and preliminary X-ray diffraction analysis of a purine nucleoside phosphorylase from Bacillus subtilis strain 168 (3679)

X-Ray Spectrometry, 2011, v. 40, n. 1, p. 19- 23 - Fator de Impacto em 2010: 1,661

Acta Crystallographica F, 2011, v. 67, n. Pt 5, p. 618622 - Fator de Impacto em 2010: 0,563

Biotechnology Letters, 2011, v.33, n.1, p. 131-137 Fator de Impacto em 2010: 1,768 3 - Analysis of thin intermediate layers by confocal muXRF+ (3601)

4 - Determination of the oxidation state by resonantRaman scattering spectroscopy (3602) Leani, J. J., Sánchez, H. J., Valentinuzzi, M. C., Pérez, C. A.

Journal of Analytical Atomic Spectrometry, 2011, v. 26 , n. 2, p. 378- 382 - Fator de Impacto em 2010: 4,372

5 - Mode of operation and low-resolution structure of a multi-domain and hyperthermophilic endo-Beta-1,3glucanase from Thermotoga petrophila (3620)

Cota, J., Alvarez, T.M., Citadini, A. P., Santos, C. R., Oliveira Neto, M., Oliveira, R. R., Pastore, G. M., Ruller, R., Prade, R. A., Murakami, M. T., Squina, F. M.

B i o c h e m i c a l a n d B i o p hys i c a l Re s e a rc h Communications, 2011, v.406, n.4, p. 590-594 - Fator de Impacto em 2010: 2,595

6 - Structural basis for branching-enzyme activity of glycoside hydrolase family 57: structure and stability studies of a novel branching enzyme from the hyperthermophilic archaeon Thermococcus Kodakaraensis KOD1 (3631)

Santos, C. R., Tonoli, C. C. C., Trindade, D. M., Betzel, C., Takata, H., Kuriki, T., Kanai, T., Imanaka, T., Arni, R. K., Murakami, M. T.

Proteins - Structure Function and Bioinformatics, 2011, v.79, n.2, p.547-557 - Fator de Impacto em 2010: 2,813 128 | ACTIVITY REPORT 2011

Martins, N. H., Meza, A. N., Santos, C. R., Giuseppe, P. O., Murakami, M. T.

10 - Molecular adaptability of nucleoside diphosphate kinase b from Trypanosomatid parasites: stability, oligomerization and structural determinants of nucleotide binding (3706)

Souza, T.A.C.B., Trindade, D. M., Tonoli, C. C. C., Santos, C. R., Ward, R. J., Arni, R. K., Oliveira, A. H. C., Murakami, M. T.

Molecular BioSystems, 2011, v.7, n.7, p. 2189-2195 - Fator de Impacto em 2010: 3,825

11 - Plant pathogenic bacteria utilize bio�ilm growthassociated repressor (BigR), a novel winged-helix redox switch, to control hydrogen sul�ide detoxi�ication under hypoxia (3725)

Guimarães, B. G., Barbosa, R. L., Soprano, A. S., Campos, B. M., de Souza, T. A., Tonoli, C. C. C., Paes Leme, A. F., Murakami, M. T., Benedetti, C. E.

Journal of Biological Chemistry, 2011, v. 286, n. 29, p. 26148-26157 - Fator de Impacto em 2010: 5,328 12 - Acessing the hidden lamellar nanostructure of semi-crystalline nascent polymers by small-angle X-ray scattering contrast variation (3796)

Westfahl Jr., H., Cardoso, M. B.

Journal of Applied Crystallography, 2011, v. 44, n.5, p. 1123-1126 - Fator de Impacto em 2010: 3,794


ARTICLES PUBLISHED IN INDEXED JOURNALS

13 - Blue-phase liquid-crystal mixtures and their induced stabilization by photopolymerization (3810)

3. In collaboration

Journal of the Society Information Display, 2011, v.19, n.11, p.781-786 - Fator de Impacto em 2010: 0,867

Silva, S. M. L., Coelho, L. N., Malachias, A., Pérez, C. A., Pesquero, J. L., Magalhães-Paniago, R., de Oliveira, M. C.

Ely, F., Santos, L.Q., Bechtold, I.H., Eccher, J., Gallardo, H., Zagonel, L. F.

14 - Size-selective silver nanoparticles: future of biomedical devices with enhanced bactericidal properties (3833) Dal Lago, V., Oliveira, L. F. de, Gonçalves, K. de A., Kobarg, J., Cardoso, M. B.

Journal of Materials Chemistry, 2011, v.21, n. 33 , p.12267-12273 - Fator de Impacto em 2010: 5,101

15 - The crystal structure of necrosis- and ethyleneinducing protein 2 from the causal agent of cacao’s Witches’ Broom disease reveals key elements for its activity (3926)

Zaparoli, G., Barsottini, M.R.O., Oliveira, J.F., Dyszy, F., Teixeira, P.J.P.L., Barau, J.G., Garcia, O., Costa Filho, A. J., Ambrosio, A. L. B., Pereira, G. A. G., Dias, S. M. G.

Biochemistry, 2011, v. 50, n. 45, p.9901-9910 - Fator de Impacto em 2010: 3,226

16 - Structure of a novel thermostable GH51 alphaL-arabinofuranosidase from Thermotoga petrophila RKU-1 (3942) Souza, T.A.C.B., Santos, C. R., Oldiges, D. P., Ruller, R., Prade, R., Squina, F. M., Murakami, M. T.

Protein Science, 2011, v. 20, n. 9, p. 1632-1637 - Fator de Impacto em 2010: 2,741 17 - Lowering the synthesis temperature of Ni2P/SiO2 by palladium addition (3996)

Silva, V. T., Sousa, L. A., Amorin, R. M., Andrini, L., Figueroa, S. J. A., Requejo, F. G., Vicentin, F. C.

Journal of Catalysis, 2011, v. 279, n. 1, p. 88-102 Fator de Impacto em 2010: 5,415

2. Associated Researchers

18 - Characterization of ultra-thin �ilms of Pd deposited on Au (111) (3629)

Pancotti, A., Nascente, P. A. P., Siervo, A. de, Landers, R., Carazzolle, M. F., Tallarico, D. A., Kleiman, G. G.

Topics in Catalysis, 2011, v.54, n.1-4, p. 70-76 - Fator de Impacto em 2010: 2,359 19 - Ordered oxide surfaces on metals: chromium oxide (3656) Pancotti, A., Siervo, A. de, Carazzolle, M. F., Landers, R., Kleiman, G. G.

Topics in Catalysis, 2011, v. 54, n. 1-4, p.90-96 - Fator de Impacto em 2010: 2,359

20 - Study of the structural organization of cyclodextrinDNA complex loaded anionic and pH-sensitive liposomes (3621) Chemical Physics Letters, 2011, v. 506, n. 1-3, p. 6670 - Fator de Impacto em 2010: 2,28 21 - Structure-property relations in crystalline L-leucine obtained from calorimetry, X-rays, neutron and Raman scattering (3630)

Façanha Filho, P. F., Jiao, X., Freire, P. T. C., Lima Jr., J. A., dos Santos, A. O., Henry, P. F., Yokaichiya, F., Kremner, E., Bordallo, H. N.

Physical Chemistry Chemical Physics (PCCP), 2011, v. 13,n. 14 , p. 6576-6583 - Fator de Impacto em 2010: 3,453 22 - Double strain state in a single GaN/A1N nanowire: probing the core-shell effect by ultraviolet resonant Raman scattering (3632)

Laneauville, V., Demangeot, F., Pechou, R., Salles, P., Ponchet, A., Jacopin, G., Rigutti, L., Bugallo, A. de L., Tchernycheva, M., Julien, F. H., March, K., Zagonel, L. F., Songmuang, R.

Physical Review B, 2011, v.83, n. 11, p. 115417-1-6 - Fator de Impacto em 2010: 3,772 23 - Crystallization and preliminary X-ray diffraction analysis of a class II phospholipase D from Loxosceles intermedia venom (3636)

Ullah, A., Giuseppe, P. O., Murakami, M. T., Silva, D. T., Wille, A. C. M., Chaves-Moreira, D., Gremski, L. H., da Silveira, R. B., Sennf-Ribeiro, A., Chaim, O. M., Veiga, S. S., Arni, R. K.

Acta Crystallographica F, 2011, v. 67, 234-236 - Fator de Impacto em 2010: 0,563 24 - Molecular cloning and biochemical characterization of a myotoxin inhibitor from Bothrops alternatus snake plasma (3639)

Santos-Filho, N. A., Fernandes, C. A. H., Menaldo, D. L., Magro, A. J., Fortes-Dias, C. L., Estevão-Costa, M. I., Fontes, M. R. M., Santos, C. R., Murakami, M. T., Soares, A. M.

Biochimie, 2011, v.93, n.3, p. 583-592 - Fator de Impacto em 2010: 3,787 2 5 - Su p ra m o l e c u l a r a s s e m b l y o f b i o hyb r i d photoconversion systems (3640)

Cardoso, M. B., Smolensky, D., Heller, W. T., Hong, K., O’Neill, H.

Energy & Environmental Science, 2011, v. 4, p. 181188 - Fator de Impacto em 2010: 9,488 26 - Synchrotron radiation X-ray micro�luorescence techniques and biological applications (3641) Lopes, R. T., Lima, I., Pereira, G. R., Pérez, C. A.

Pramana - Journal of Physics, 2011, v. 76, n. 2, p. 271-279 - Fator de Impacto em 2010: 0,561 Brazilian Synchrotron Light Laboratory | 129


ARTICLES PUBLISHED IN INDEXED JOURNALS

27 - Nanometer scale spectral imaging of quantum emitters in nanowires and its correlation to their atomically resolved structure (3642) Zagonel, L. F., Mazzucco, S., Tencé, M., March, K., Bernard, R., Laslier, B., Jacopin, G., Tchernycheva, M., Rigutti, L., Julien, F. H., Songmuang, R., Kociak, M.

Nano Letters, 2011, v. 11, n. 2, p. 568- 573 - Fator de Impacto em 2010: 12,218 28 - Study of roughness evolution and layer stacking faults in short-period atomic layer deposited HfO2/Al2O3 multilayers (3676)

de Pauli, M., Malachias, A., Westfahl Jr., H., Bettini, J., Ramirez, A. J., Mei, Y. F., Schmidt, O. G.

Journal of Applied Physics, 2011, v.109, n. 6, p. 063524-1-7 - Fator de Impacto em 2010: 2,064

29 - Metallomic study on plasma samples from Nile tilapia using SR-XRF and GFAAS after separation by 2D PAGE: initial results (3680) Santos, F. A., Lima, P. M., Neves, R. de C. F., Moraes, P. M., Pérez, C. A., Silva, M. O. A., Arruda, M. A. Z., Castro, G. R., Padilha, P. M.

Microchimica Acta, 2011, v. 46, n. 1-2, p. 43-49 - Fator de Impacto em 2010: 2,578 30 - Biochemical and structural characterization of a Beta-1,3-1,4-glucanase from Bacillus subtilis 168 (3682) Furtado, G. P., Ribeiro, L. F., Santos, C. R., Tonoli, C. C. C., Oliveira, R. R., de Souza, A. R., Murakami, M. T., Ward, R. J.

Process Biochemistry, 2011, v.46, n.5, p.1202-1206 - Fator de Impacto em 2010: 2,648

31 - Plantain and banana starches: granule structural characteristics explain the differences in their starch degradation patterns (3698)

Soares, C. A., Peroni-Okita, F. H. G., Cardoso, M. B., Shitakubo, R., Lajolo, F. M., Cordenunsi, B. R.

Journal of Agricultural and Food Chemistry, 2011, v. 59, n.12, p. 6672- 6681 - Fator de Impacto em 2010: 2,816 32 - Pressure and chemical substitution effects in the local atomic structure of BaFe2As2 (3699)

Granado, E., Mendonça-Ferreira, L., Garcia, F., Azevedo, G. de M., Fabris, G. F. L., Bittar, E. M., Adriano, C., Garitezi, T. M., Rosa, P. F. S., Bufaiçal, L., Avila, M. A., Terashita, H., Pagliuso, P. G.

Physical Review B, 2011, v. 83, n. 184508-1-6 - Fator de Impacto em 2010: 3,772

33 - Structure of a novel class II phospholipase D: catalytic cleft is modi�ied by a disulphide bridge (3716) Giuseppe, P. O., Ullah, A., Silva, D. T., Gremski, L. H., Wille, A. C. M., Moreira, D. C., Ribeiro, A. S., Chaim, O. M., Murakami, M. T., Veiga, S. S., Arni, R. K.

B i o c h e m i c a l a n d B i o p hys i c a l Re s e a rc h Communications, 2011, v. 409, n.4, n. 622-627 Fator de Impacto em 2010: 2,595 130 | ACTIVITY REPORT 2011

34 - Spin liquid in a single crystal of the frustrated diamond lattice antiferromagnet CoAl2O4 (3758)

Zaharko, O., Christensen, N. B., Cervellino, A., Tsurkan, V., Maljuk, A., Stuhr, U., Niedermayer, C., Yokaichiya, F., Argyriou, D. N., Boehm, M., Loidl, A.

Physical Review B, 2011, v. 84, n. 9, p. 094403-1-8 Fator de Impacto em 2010: 3,772 35 - Stability of the ferromagnetic ground state of La2MnNiO6 against large compressive stress (3761)

Haskel, D., Fabbris, G., Souza Neto, N. M., van Veenendaal, M., Shen, G., Smith, A. E., Subramanian, M. A.

Physical Review B, 2011, v. 84, n. 10, p. 100403-1-4 - Fator de Impacto em 2010: 3,772

36 - Relationship between trace elemental composition in Fraxinus pennsylvanica bark and the incidence of some respiratory diseases in Cordoba, Argentina (3782) Wannaz, E. D., Carreras, H. A., Pérez, C. A., Pignata, M. L.

International Journal of Environment and Health, 2011, v. 5, n. 1-2, p. 60-71 - Fator de Impacto em 2010: 0

37 - In-situ microtomographic characterization of singlecavity growth during high-temperature creep of leaded brass (3786) Isaac, A., Dzieciol, K., Sket, F., Borbély, A.

Metallurgical and Materials Transactions A, 2011, v. 42, n. 10, p. 3022-3030 - Fator de Impacto em 2010: 1,721 38 - Characterizatrion of creep and creep damage by in-situ microtomography (3787)

Borbély, A., Dzieciol, K., Sket, F., Isaac, A., Michiel, M., Buslaps, Th., Kaysser-Pyzalla, A. R.

JOM-US, 2011, v. 63, n. 7, p. 78-84 - Fator de Impacto em 2010: 1,179

39 - Sol-gel preparation of aminopropyl-silica-magnesia hybrid materials (3804) Brambilla, R., Poisson, J., Radtke, C., Miranda, M. S. L., Cardoso, M. B., Butler, I. S., dos Santos, J. H. Z.

Journal of Sol-Gel Science and Technology, 2011, v. 59, n. 1,p. 135-144 - Fator de Impacto em 2010: 1,525 40 - Bandwidth-driven nature of the pressure-induced metal (3829)

Ramos, A. Y., Souza Neto, N. M., Tolentino, H. C. N., Bunau, O., Joly, Y., Grenier, S., Itié, J.-P., Flank, A.-M., Lagarde, P., Caneiro, A.

EPL, 2011, v.96, n.3, p. 36002-p1-36002-p6 - Fator de Impacto em 2010: 2,753

41 - Co-substitution effects on the Fe valence in the BaFe2As2 superconducting compound: a study of hard X-ray absorption spectroscopy (3930)

Bittar, E. M., Adriano, C., Garitezi, T. M., Rosa, P. F. S., Mendonça-Ferreira, L., Garcia, F., Azevedo, G. de M., Pagliuso, P. G., Granado, E.

Physical Review Letters, 2011, v. 107, n.26, 2674021-3 - Fator de Impacto em 2010: 7,622


ARTICLES PUBLISHED IN INDEXED JOURNALS

42 - Compressibility study of quaternary phospholipid blend monolayers (3935) Cavalcanti, L. P., Konovalov, O., Tho, I., Fossheim, S., Brandl, M.

Colloids and Surfaces B, 2011, v.85, n.2, p.153-160 - Fator de Impacto em 2010: 2,78

43 - Properties of magnetic nanodots with perpendicular anisotropy (3938) Novais, E. R. P., Landeros, P., Barbosa, A. G. S., Martins, M. D., Garcia, F., Guimarães, A. P.

Journal of Applied Physics, 2011, v. 110, 053917-16 - Fator de Impacto em 2010: 2,064

44 - Effect of Si doping and applied pressure upon magnetostructural properties of TB5(SixGe1-x)4 magnetocaloric compounds (3939)

Tseng, P. H., Ma, H.-J., Yang, C.-Y., Mudryk, Y., Pecharsky, V. K., Gschneidner Jr., K. A., Souza Neto, N. M., Haskel, D.

Physical Review B, 2011, v. 83, n. 10, 104419-1-7 Fator de Impacto em 2010: 3,772

4. User publications

51 - Hydrogen puri�ication for fuel cell using CuO/CeO2 - Al2O3 catalyst (3355) Maciel, C. G., Profeti, L. P. R., Assaf, E. M., Assaf, J. M.

Journal of Power Sources, 2011, v. 196, n. 2, p. 747753 - Fator de Impacto em 2010: 4,283

52 - Particle size effect for ethanol electro-oxidation on Pt/C catalysts in half-cell and in a single direct ethanol fuel cell (3604) Perez, J., Paganin, V. A., Antolini, E.

Journal of Electroanalytical Chemistry, 2011, v. 654, n. 1-2, p. 108-115 - Fator de Impacto em 2010: 2,732

53 - Persistence length, mass fractal, and branching in the aggregating of Vinyltriethoxysilane-Derived Organic/ Silica Hybrids (3608) Donatti, D. A., Awano, C. M., de Vicente, F. S., Ibanez Ruiz, A., Vollet, D. R.

45 - 3D elemental distribution images in biological samples by XRFmuCT (3940)

Journal of Physical Chemistry C, 2011, v. 115, n.3, p. 667- 671 - Fator de Impacto em 2010: 4,52

X-Ray Spectrometry, 2011, v. 40, n. 4, p. 260-264 Fator de Impacto em 2010: 1,661

Souza Jr., F. G., Orlando, M. T. D., Michel, R. C., Pinto, J. C., Cosme, T., Oliveira, G. E.

Pereira, G. R., Rocha, H. S., Calza, C., Anjos, M. J. dos, Lima, I., Pérez, C. A., Lopes, R. T.

46 - 3D elemental distribution images by XRFmuCT at LNLS-Brazil (3941)

Pereira, G. R., Rocha, H. S., Calza, C., Anjos, M. J. dos, Lima, I., Pérez, C. A., Lopes, R. T.

Nuclear Instr and Meth in Physics Research A, 2011, v. 652, n.1, p. 684-686 - Fator de Impacto em 2010: 1,142

47 - The water effect on the kinetics of the bovine liver catalase (3950) Seixas, F. A. V., Silva, M. R., Murakami, M. T., Tosqui, P., Colombo, M. F.

Protein and Peptide Letters, 2011, v. 18, n. 9, p. 879885 - Fator de Impacto em 2010: 1,849 48 - Rolled-up tubes and cantilevers by releasing SrRuO3Pr0.7Ca0.3MnO3 nanomembranes (3969)

Deneke, C., Wild, E., Boldyreva, K., Baunack, S., Cendula, P., Mönch, J. I., Simon, M., Malachias, A., Dörr, K., Schmidt, O. G.

Nanoscale Research Letters, 2011, v. 6, n. 1, p. 6211-8 - Fator de Impacto em 2010: 2,557

49 - Characterization of creep and creep damage by insitu microtomography (3977) Borbély, A., Dzieciol, K., Sket, F., Isaac, A., Michiel, M., Buslaps, T., Kaysser-Pyzalla, A. R.

JOM-US, 2011, v.63, n.7, p.78-84 - Fator de Impacto em 2010: 1,179

50 - Hybrid organic/inorganic molecular heterojunctions based on strained nanomembranes (3979) Bufon, C. C. B., Espinoza, J. D. A., Thurmer, D. J., Bauer, M., Deneke, C., Zschieschang, U., Klauk, H., Schmidt, O. G.

Nano Letters, 2011, v. 11, n. 9, p. 3727-3733 - Fator de Impacto em 2010: 12,218

54 - Effect of pressure on the structure and electrical conductivity of cardanol-furfural-polyaniline blends (3611) Journal of Applied Polymer Science, 2011, v. 119, n. 5, p. 2666-2673 - Fator de Impacto em 2010: 1,24

55 - The binding of synthetic triiodo L-thyronine analogs to human transthyretin: molecular basis of cooperative and non-cooperative ligand recognition (3614) Trivella, D. B. B., Sairre, M. I., Foguel, D., Lima, L. M. T. R., Polikarpov, I.

Journal of Structural Biology, 2011, v. 173, n. 2, p. 323- 332 - Fator de Impacto em 2010: 3,497

56 - Photostability of gas- and solid-phase biomolecules within dense molecular clouds due to soft X-rays (3616) Pilling, S., Andrade, D. P. P., Marinho, R. R. T., Boechat-Roberty, H. M. , Coutinho, L. H., de Castilho, R. B., Souza, G. G. B. de, Cavasso-Filho, R. L., Lago, A. F., Naves de Brito, A.

Monthly Notices of the Royal Astronomical Society, 2011, v. 411, n. 4, p. 2214- 2222 - Fator de Impacto em 2010: 4,888 57 - Tetragonal-cubic phase boundary in nanocrystalline ZrO2-Y2O3 solid solutions synthesized by gel-combustion (3617)

Fábregas, I. O., Craievich, A. F., Fantini, M. C. A., Millen, R. P., Temperini, M. L. A., Lamas, D. G.

Journal of Alloys and Compounds, 2011, v. 509, n. 16, p. 5177-5182 - Fator de Impacto em 2010: 2,134 58 - XAS characterization of the RuO2-Ta2O5 system local (crystal) structure (3624) Ribeiro, J., Tremiliosi-Filho, G., Olivi, P., de Andrade, A. R.

Materials Chemistry and Physics, 2011, v. 125, n. 3, p. 449-460 - Fator de Impacto em 2010: 2,353 Brazilian Synchrotron Light Laboratory | 131


ARTICLES PUBLISHED IN INDEXED JOURNALS

59 - Conformational stability of peanut agglutinin using small angle X-ray scattering (3627)

67 - Structural basis for both pro- and anti-in�lammatory response induced by mannose-speci�ic legume lectin from Cymbosema roseum (3685)

60 - Insight into copper-based catalysts: microwaveassisted morphosynthesis, in situ reduction studies, and dehydrogenation of ethanol (3628)

Biochimie, 2011, v. 93, n. 5, p. 806-816 - Fator de Impacto em 2010: 3,787

Campana, P. T., Barbosa, L. R. S., Itri, R.

International Journal of Biological Macromolecules, 2011, v. 48, n. 3, p. 398-402 - Fator de Impacto em 2010: 2,502

Volanti, D. P., Sato, A. G, Orlandi, M. O., Bueno, J. M. C., Longo, E., Andrés, J.

ChemCatChem, 2011, v. 3, n.5 , p. 839-843 - Fator de Impacto em 2010: 3,345 61 - Structural properties and reduction behavior of novel nanostructured Pd/Gadolinia-doped ceria catalysts with tubular morphology (3654)

Muñoz, F. F., Cabezas, M. D., Acuña, L. M., Leyva, A. G., Baker, R. T., Fuentes, R. O.

Journal of Physical Chemistry C, 2011, v. 115, n. 17, p. 8744-8752 - Fator de Impacto em 2010: 4,52

62 - SiO2/SnO2/Sb2O5 microporous ceramic material for immobilization of Meldola’s blue: application as an electrochemical sensor for NADH (3658) Canevari, T. C., Vinhas, R. C. G., Landers, R., Gushikem, Y.

Biosensors & Bioelectronics, 2011, v. 26, n. 5, p. 2402- 2406 - Fator de Impacto em 2010: 5,361 63 - Activity of SiDbCl in the electrooxidation of ascorbic acid, dopamine, and uric acid (3659) Arguello, J., Magosso, H. A., Canevari, T. C., Landers, R., Gushikem, Y.

Electroanalysis, 2011, v. 23, p. 334-338 - Fator de Impacto em 2010: 2,721

64 - Crystallization and preliminary X-ray diffraction analysis of a Lys49-phospholipase A2 complexed with caffeic acid, a molecule with inhibitory properties against snake venoms (3681) Shimabuku, P. S., Fernandes, C. A. H., Magro, A. J., Costa, T. R., Soares, A. M., Fontes, M. R. M.

Acta Crystallographica F, 2011, v. 67, n. Pt 2, p. 249252 - Fator de Impacto em 2010: 0,563

65 - Structural, functional, and bioinformatics studies reveal a new snake venom homologue phospholipase A2 class (3683)

dos Santos, J. I., Cintra-Francischinelli, M., Borges, R. J., Fernandes, C. A. H., Pizzo, P., Cintra, A. C. O., Braz, A. S. K., Soares, A. M., Fontes, M. R. M.

Proteins - Structure Function and Bioinformatics, 2011, v. 79, n. 1, p. 61-78 - Fator de Impacto em 2010: 2,813 66 - Crystal structure of Bn IV in complex with myristic acid: A Lys49 myotoxic phospholipase A2 from Bothrops neuwiedi venom (3684)

Delatorre, P., Rocha, B. A. M., Santi-Gadelha, T., Gadelha, C. A. de A., Toyama, M., Cavada, B. S.

Biochimie, 2011, v. 93, n. 3, p. 513-518 - Fator de Impacto em 2010: 3,787 132 | ACTIVITY REPORT 2011

Rocha, B. A. M., Delatorre, P., Oliveira, T. M., Benevides, R. G., Pires, A. F., Sousa, A. A. S., Souza, L. A. G., Assreuy, A. M. S., Debray, H., de Azevedo Jr., W. F., Sampaio, A. H., Cavada, B. S.

68 - X-ray phase measurements as a probe of small structural changes in doped nonlinear optical crytals (3687) Morelhão, S. L., Remédios, C. M. R., Freitas, R. O., dos Santos, A. O.

Journal of Applied Crystallography, 2011, v. 44, n. 1, p. 93-101 - Fator de Impacto em 2010: 3,794

69 - Characterization of nanostructured epoxy networks modi�ied with isocyanate-terminated liquid polybutadiene (3688) Soares, B. G., Dahmouche, K., Lima, V. D., Silva, A. A., Caplan, S. P. C., Barcia, F. L.

Journal of Colloid and Interface Science, 2011, v. 358, n. 2, p. 338-346 - Fator de Impacto em 2010: 3,066

70 - Magnetic and structural properties of fcc/hcp bicrystalline multilayer Co nanowire arrays prepared by controlled electroplating (3692) Pirota, K. R., Béron, F., Zanchet, D., Rocha, T. C. R., Navas, D., Torrejón, J., Vazquez, M., Knobel, M.

Journal of Applied Physics, 2011, v. 109, n. 8, p. 083919-1-6 - Fator de Impacto em 2010: 2,064

71 - ZnFeO4 Nanoparticles for ferro�luids: a combined XANES and XRD study (3693)

Gomes, J. A., Colaço, M. V., Azevedo, G. de M., Porto, I. M., Depeyrot, J., Mestnik-Filho, J., Gerlach, R. F., Silva, G. J. da, Costa, F. N., Tourinho, F. A., Braz, D., Droppa Jr., R., Perzynski, R.

Journal of Magnetism and Magnetic Materials, 2011, v. 323, n. 10, p. 1203-1206 - Fator de Impacto em 2010: 1,689 72 - A component of the Xanthomonadaceae type IV secretion system combines a VirB7 motif with a N0 domain found in outer membrane transport proteins (3704)

Souza, D. P., Andrade, M. O., Alvarez-Martinez, C. E., Arantes, G. M., Farah, C. S., Salinas, R. K.

PLoS Pathogens, 2011, v. 7, n. 5, p. e1002031-1-18 - Fator de Impacto em 2010: 9,079

73 - Amyloid �ibril formation by circularly permuted and C-terminally deleted mutants (3707) Corrêa, D., H. do A., Ramos, C. H. I.

International Journal of Biological Macromolecules, 2011, v. 48, n. 4, p. 583-588 - Fator de Impacto em 2010: 2,502


ARTICLES PUBLISHED IN INDEXED JOURNALS

74 - Crystal structure determination and dynamic studies of Mycobacterium tuberculosis Cytidine deaminase in complex with products (3708)

82 - Electrochemical study of o-toluidine blue impregnated in mesoporous silica chanels (3740)

Archives of Biochemistry and Biophysics, 2011, v. 509, n. 1, p. 108-115 - Fator de Impacto em 2010: 3,022

83 - Surface structure determination of Pd on W(100) using X-ray photoelectron diffraction (3742)

Sánchez-Quitian, Z., Timmers, L. F. S. M., Caceres, R. A., Rehm, J. G., Thompson, C. E., Basso, L. A., de Azevedo Jr., W. F., Santos, D. S. dos

75 - The crystal complex of phosphofructokinase-2 of Escherichia coli with fructose-6-phosphate. Kinetic and structural analysis of the allosteric ATP inhibition (3712) Cabrera, R., Baez, M., Pereira, H. M., Caniuguir, A., Garratt, R. C., Babul, J.

Journal of Biological Chemistry, 2011, v. 286, n. 7, p. 5774-5783 - Fator de Impacto em 2010: 5,328

76 - Crystallization and preliminary X-ray diffraction analysis of recombinant chlorocatechol 1,2-dioxygenase from Pseudomonas putida (3713) Rustiguel, J. K. R., Pinheiro, M. P., Araújo, A. P. U., Nonato, M. C.

Acta Crystallographica F, 2011, v. 67, Pt. 4, p. 507509 - Fator de Impacto em 2010: 0,563 77 - A rational protocol for the successful crystallization of L-amino-acid oxidase from Bothrops atrox (3714) Alves, R. M., Feliciano, P. R., Sampaio, S. V., Nonato, M. C.

Acta Crystallographica F, 2011, v. 67, Pt. 4, p. 472478 - Fator de Impacto em 2010: 0,563 78 - In-Situ monitoring of the structure of a goethitebased catalyst during methane oxidation by X-ray absorption near-edge structure (XANES) spectroscopy assisted by chemometric methods (3735)

Nunes, C. A., Resende, E. C., Guimarães, I. R., Guerreiro, M. C., Anastácio, A. S.

Applied Spectroscopy, 2011, v. 65, n. 6, n. 692-697 - Fator de Impacto em 2010: 1,729

79 - Thermodynamic and structural characterization of zwitterionic micelles of the membrane protein solubilizing amidosulfobetaine surfactants ASB-14 and ASB-16 (3736)

D’Andrea, M. G., Domingues, C. C., Malheiros, S. V. P., Gomes Neto, F., Barbosa, L. R. S., Itri, R., Almeida, F. C. L., Paula, E., Bianconi, M. L.

Langmuir, 2011, v. 27, n. 13, p. 8248-8256 - Fator de Impacto em 2010: 4,268

80 - Comparison between Einstein and Debye models for an amorphous Ni46Ti54 alloy produced by mechanical alloying investigated using extended X-ray absorption �ine structure and cumulant expansion (3738) Machado, K. D.

Journal of Chemical Physics, 2011, v. 134, n. 6, p. 064503-1-9 - Fator de Impacto em 2010: 2,92

81 - EXAFS and cumulant expansion studies of an amorphous Se90P10 alloy produced by mechanical alloying (3739) Machado, K. D., Oliveira, E. C., Deflon, E., Stolf, S. F.

Solid State Communications, 2011, v. 151, n.18 , p.1280-1284 - Fator de Impacto em 2010: 1,979

Martines, M. A. U., do Carmo, D. R., Castro, G. R., Caetano, L.

Journal of Sol-Gel Science and Technology, 2011, v. 59, n.1, p.188-193 - Fator de Impacto em 2010: 1,525

Lussani, F. C., Siervo, A. de, Figueiredo, J. J. S., Landers, R., Pancotti, A.

Surface Science, 2011, v. 605, n. 21-22 , p. 1900-1905 - Fator de Impacto em 2010: 2,01

84 - An ef�icient synthesis route of Na2V6O16.nH2O nanowires in hydrothermal conditions (3750) Avansi Jr., W., Ribeiro, C., Leite, E. R., Mastelaro, V. R.

Materials Chemistry and Physics, 2011, v. 127, n. 1-2, p. 56-61 - Fator de Impacto em 2010: 2,353

85 - Presence of excited electronic state in CaWO4 crystals provoked by a tetrahedral distortion: An experimental and theoretical investigation (3752)

Gracia, L., Longo, V. M., Cavalcante, L. S., Beltrán, A., Avansi Jr., W., Li, M. S., Mastelaro, V. R., Varela, J. A., Longo, E., Andrés, J.

Journal of Applied Physics, 2011, v. 110, n. 4, p. 043501-1-11 - Fator de Impacto em 2010: 2,064

86 - Structural and properties of nanocrystalline WO3/ TiO2-based humidity sensors elements prepared by high energy activation (3753)

Rocha, K. O., Zanetti, S. M.

Sensors and Actuators B, 2011, v.,157, n. 2, p. 654661 - Fator de Impacto em 2010: 3,368

87 - Rapid solidi�ication and phase stability evaluation of Ti-Si-B alloys (3754) Candioto, K. C. G., Nunes, C. A., Coelho, G. C., Suzuki, P. A., Gabriel, S. B.

Journal of Alloys and Compounds, 2011, v. 509, n.17, p. 5263-5268 - Fator de Impacto em 2010: 2,134 88 - Formation of one dimensional linear chains by Ir-Ir bonds in cis-dicarbonyldichloroiridate (I) (3755)

Bikiel, D. E., Ramallo-López, J. M., Requejo, F. G., Oña, O. B., Ferraro, M. B., Facelli, J. C., Doctorovich, F.

Polyhedron, 2011, v. 30, n. 2, p. 221-227 - Fator de Impacto em 2010: 2,033

89 - Ge-modi�ied Pt/SiO2 catalysts used in preferential CO oxidation (CO-PROX) (3756) Bideberripe, H. P., Ramallo-López, J. M., Figueroa, S. J. A., Jaworski, M. A., Casella, M. L., Siri, G. J.

Catalysis Communications, 2011, v.12, n.14, p.12801285 - Fator de Impacto em 2010: 2,827 90 - “Naked” gold nanoparticles supported on HOPG: melanin functionalization and catlytic activity (3757)

González Orive, A., Grumelli, D., Vericat, C., Ramallo-López, J. M., Giovanetti, L., Benitez, G., Fonticelli, M. H., Requejo, F. G., Hernández Creus, A., Salvarezza, R. C.

Nanoscale, 2011, v. 3, n. 4, p. 1708-1716 - Fator de Impacto em 2010: 4,109 Brazilian Synchrotron Light Laboratory | 133


ARTICLES PUBLISHED IN INDEXED JOURNALS

91 - Membrane morphology modi�ications induced by hydroquinones (3760) Funari, S. S., Rebbin, V., Marzorati, L., di Vitta, C.

Langmuir, 2011, v.27, n. 13, p. 8257-8262 - Fator de Impacto em 2010: 4,268 92 - Photocatlytic activity of TiO2 thin �ilms deposited by cathodic arc (3763)

Kleiman, A., Márquez, A., Vera, M. L., Meichtry, J. M., Litter, M. I.

Applied Catalysis B, 2011, v. 101, n. 3-4, p. 676-681 - Fator de Impacto em 2010: 4,749

93 - Surface and structural features of Pt/CeO2-La2O3Al2O3 catalysts for partial oxidation and steam reforming of methane (3764) Mortola, V. B., Damyanova, S., Zanchet, D., Bueno, J. M. C.

Applied Catalysis B, 2011, v. 107, n. 3-4, p. 221-236 - Fator de Impacto em 2010: 4,749

94 - Structure and redox properties of Co promoted Ni/ Al2O3 catalysts for oxidative steam reforming of ethanol (3765) Andonova, S., de Ávila, C. N., Arishtirova, K., Bueno, J. M. C., Damyanova, S.

Applied Catalysis B, 2011, v. 105, n. 3-4, p. 346-360 - Fator de Impacto em 2010: 4,749

95 - Macromolecular assembly of polycystin-2 intracytosolic C-terminal domain (3766) Ferreira, F. M., Oliveira, L. C., Germino, G. G., Onuchic, J. N., Onuchic, L. F.

Proceedings of the National Academy of Sciences USA, 2011, v. 108, n. 24, p. 9833-9838 - Fator de Impacto em 2010: 9,771 96 - Multivariate analysis of the scattering pro�iles of healthy and pathological human breast tissues (3767)

100 - On the reversed crystal growth of BaZrO3 decaoctahedron: shape evolution and mechanism (3771)

Moreira, M. L., Andrés, J., Mastelaro, V. R., Varela, J. A., Longo, E.

CrystEngComm, 2011, v. 13, n. , p. 5818-5824 - Fator de Impacto em 2010: 4,006 101 - Outermost and inner-shell electronic properties of ClC(O)SCH2CH3 studied using heI photoelectron spectroscopy and synchrotron radiation (3773) Rodriguez Pirani, L. S., Erben, M. F., Geronés, M., Ma, C., Ge, M., Romano, R. M., Cavasso-Filho, R. L., Della Védova, C. O.

Journal of Physical Chemistry A, 2011, v. 115, n. , p. 5307-5318 - Fator de Impacto em 2010: 2,732 102 - Solution properties of a hydrophobically associating polyacrylamide and its polyelectrolyte derivatives determined by light scattering, small angle x-ray scattering and viscometry (3774) Maia, A. M. S., Villetti, M. A., Borsali, R., Balaban, R. C.

Journal of Brazilian Chemical Society, 2011, v. 22, n. 3, p. 489-500 - Fator de Impacto em 2010: 1,343

103 - Correlating sulfur reactivity of PtxPd1-x nanoparticles with a bimetallic interaction effect (3775) Bernardi, F., Traverse, A., Olivi, P., Alves, M. C. M., Morais, J.

Journal of Physical Chemistry C, 2011, v. 115, n. 25, p. 12243-12249 - Fator de Impacto em 2010: 4,52 104 - Chemical analysis of size-tailored magnetic colloids using slurry nebulization in ICP-OES (3777)

Sousa, M. H., da Silva, G. J., Depeyrot, J., Tourinho, F. A., Zara, L. F.

Microchemical Journal, 2011, v. 97, n.2, p. 182-187 - Fator de Impacto em 2010: 2,48

Conceição, A. L. C., Antoniassi, M., Cunha, D. M., Ribeiro-Silva, A., Poletti, M. E.

105 - Production of highly charged Ne ions by synchrotron radiation (3779)

97 - XANES-PCA analysis of Ti-species in MCM-41 mesoporous silica synthesized by different method (3768) Anunziata, O. A., Beltramone, A. R., Martinez, M. L., Giovanetti, L. J., Requejo, F. G., Lede, E. J.

106 - Sputtering onto liquids: from thin �ilms to nanoparticles (3783)

98 - On the stabilization of gold nanoparticles over silicabased magnetic supports modi�ied with organosilanes (3769)

107 - Effect of synthesis conditions on the microstructure of TEOS derived silica hydrogels synthesized by the alcohol-free sol-gel route (3784)

Nuclear Instr and Meth in Physics Research A, 2011, v. 652, n. 1, p. 870-873 - Fator de Impacto em 2010: 1,142

Applied Catalysis A, 2011, v. 397, n. 1-2, p. 22-26 Fator de Impacto em 2010: 3,383

Santos, A. C. F., Homem, M. G. P., Almeida, D. P.

Journal of Electron Spectroscopy and Related Phenomena, 2011, v. 184, n. 1-2 , p. 38-42 - Fator de Impacto em 2010: 1,75 Wender, H., Gonçalves, R. V., Feil, A. F., Migowski, P., Poletto, F. S., Pohlmann, A. R., Dupont, J., Teixeira, S. R.

Journal of Physical Chemistry C, 2011, v. 1115, n.27, p. 16362-16367 - Fator de Impacto em 2010: 4,52

Oliveira, R. L., Zanchet, D., Kiyohara, P. K., Rossi, L. M.

Jobbágy, M., Bilmes, S. A., Torriani, I., Candal, R. J.

99 - Physical characterization of high-k HfxAl1-xOy gate dielectrics prepared by ALD (3770)

108 - Structure and properties of conducting bacterial cellulose-polyaniline nanocomposites (3785)

Chemistry - A European Journal, 2011, v. 17, n. 16, p. 4626-4631 - Fator de Impacto em 2010: 5,476 Christiano, V., Adelmann, C., Kellermann, G., Verdonck, P., dos Santos Filho, S. G.

ECS Transactions, 2011, v. 39, n. 1, p.393-400 - Fator de Impacto em 2010: 0 134 | ACTIVITY REPORT 2011

Journal of Sol-Gel Science and Technology, 2011, v. 59, n. 1, p. 174-180 - Fator de Impacto em 2010: 1,525

Marins, J. A., Soares, B. G., Dahmouche, K., Ribeiro, S. J. L., Barud, H. S.

Cellulose, 2011, v. 18, n. 5, p. 1285-1294 - Fator de Impacto em 2010: 2,817


ARTICLES PUBLISHED IN INDEXED JOURNALS

109 - Purine nucleoside phosphorylase from Schistosoma mansoni in complex with ribose-1-phosphate (3791) Pereira, H. M., Oliva, G., Garratt, R. C.

Journal of Synchrotron Radiation, 2011, v. 18, n. 1, p. 62-65 - Fator de Impacto em 2010: 2,335

110 - Structural basis for selective inhibition of purine nucleoside phosphorylase from Schistosoma mansoni: kinetic and structural studies (3792) Castilho, M. S., Pereira, H. M., Oliva, G., Andricopulo, A. D.

Bioorganic & Medicinal Chemistry, 2011, v. 18, n. 4, p. 1421-1427 - Fator de Impacto em 2010: 2,978

111 - Structural characterization of supported nanocrystalline ZnO thin �ilms prepared by dip-coating (3795)

Casanova, J. R., Heredia, E., Bojorge, C. D., Cánepa, H. R., Kellermann, G., Craievich, A. F.

Applied Surface Science, 2011, v. 257, n.23, p. 1004510051 - Fator de Impacto em 2010: 1,793 112 - Determination of cobalt marker in cow ruminal �luid by EDXRF and SRTXRF (3811)

Almeida, A., Massoni, P.R., Menegário, A.A., Leite, L.C., Lanna, D.P.D., Nascimento Filho, V. F.

X-Ray Spectrometry, 2011,v.40, n.6, p.424-426 - Fator de Impacto em 2010: 1,661

113 - Structure, morphology and thermal stability of synthetic �luorine mica and its organics derivatives (3813) Souza, D.H.S., Dahmouche, K., Andrade, C.T,, Dias, M.L.

117 - Comparative Study of Different Methods for the Preparation of CoxOy/C for the Electrosynthesis of Hydrogen Peroxide (3822) Assumpção, M.H.M.T., Rascio, D. C., Ladeia, J.P.B., Souza, R.F.B., Teixeira-Neto, E., Calegaro, M. L., Oliveira, R. T. S., Gaubeur, I,, Lanza, M.R.V., Santos, M. C. dos

International Journal of Electrochemical Science, 2011, v.6, n. 6, p.1586-1596 - Fator de Impacto em 2010: 2,808 118 - Evidence of defect-induced ferromagnetism in ZnFe2O4 thin �ilms (3827)

Rodriguez Torres, C. E., Golmar, F., Ziese, M., Esquinazi, P., Heluani, S. P.

Physical Review B, 2011, v.84, n.6, p.064404-1-9 Fator de Impacto em 2010: 3,772 119 - Self-assembly of polyon-surfactant ion complex salts in mixtures with water and n-alcohols (3828) Bernardes, J. S., Picullel, L., Loh, W.

Journal of Physical Chemistry B, 2011, v.115, 90509058 - Fator de Impacto em 2010: 3,603

120 - Structural characterization and in vivo evaluation of retinyl palmitate in non-ionic lamellar liquid crystalline system (3831) Chorilli, M., Prestes, P.S., Rigon, R.B., Leonardi, G.R., Chiavacci, L. A., Sarmento, V. H. V., Oliveira, A. G. de, Scarpa, M.V.

Colloids and Surfaces B, 2011,v.85, n. 2, p. 182-188 - Fator de Impacto em 2010: 2,78 121 - Study of the morphology exhibited by linear segmented polyurethane (3834) Pereira, I. M., Oréfice, R. L.

Macromolecular Symposia, 2011, v.299/300, n.1, p.190-198 - Fator de Impacto em 2010: 0

Applied Clay Science, 2011, v.54, n. 3-4, p.226-234 - Fator de Impacto em 2010: 2,303

122 - Study of Sm2O3-doped CeO2-Al2O3-supported Pt catalysts for partial CH4 oxidation (3835)

Silva, A. A., Dahmouche, K., Soares, B. G.

123 - Biodegradable polyurethane nanocomposites containing dexamethasone for ocular route (3836)

114 - Nanostructure and dynamic mechanical properties of silane-functionalized montmorillonite/epoxy nanocomposites (3814)

Applied Clay Science, 2011, v.54, n.2, p.151-158 Fator de Impacto em 2010: 2,303 115 - Elemental concentration and source identi�ication of PM10 and PM2.5 by SR-XRF in Córdoba City, Argentina (3817)

López, M.L., Ceppi, S., Palancar, G.G., Olcese, L.E., Tirao, G.

Atmospheric Environment, 2011, v.45, n.31, p.54505457 - Fator de Impacto em 2010: 3,226

116 - Solvent-free chromium catalyzed aerobic oxidation of biomass-based alkenes as a route to valuable fragrance compounds (3819)

Robles-Dutenhefner, P. A., Brandão, B.N.S., Sousa, L.F., Gusevskaya, E. V.

Applied Catalysis A, 2011, v.399, n.1-2, p.172-178 Fator de Impacto em 2010: 3,383

Duarte, R. B., Damyanova, S., Oliveira, D. C., Marques, C. M. P., Bueno, J. M. C.

Applied Catalysis A, 2011, v. 399, n.1-2, p. 134-145 - Fator de Impacto em 2010: 3,383

Silva, G.R., Cunha Jr., A. da S., Behar-Cohen, F., Ayres, E., Oréfice, R. L.

Materials Science and Engineering C, 2011, v.31, n.2 p.141-422 - Fator de Impacto em 2010: 2,178

124 - Polyurethanes as supports for human retinal pigment epithelium cell growth (3837)

Naud, M.C., Silva, G.R., Cunha Jr., A. da S., Saliba, J.B., Berdugo, M., Goldenberg, B.T., Ayres, E., Oréfice, R. L., Behar-Cohen, F.

Internacional Journal Arti�icial Organs, 2011, v.34, n.2, p.198-209 - Fator de Impacto em 2010: 1,503

125 - Internal residual stresses in sintered and commercial low expansion Li2O-Al2O3-SiO2 glass-ceramics (3838) Serbena, F.C., Soares, V.O., Peitl, O., Pinto, H., Muccillo, E. N. S., Zanotto, E.D.

Journal of the American Ceramic Society, 2011, v. 64, n. 4, p.1206-1214 - Fator de Impacto em 2010: 2,167 Brazilian Synchrotron Light Laboratory | 135


ARTICLES PUBLISHED IN INDEXED JOURNALS

126 - Internal residual stresses in partially crystallized photo-thermo-refractive glass (3839) Serbena, F.C., Souza, G.P., Zanotto, E.D., Lumeau, J., Glebova, L., Glebov, L.B.

Journal of the American Ceramic Society, 2011, v.94,n.3, p.671-674 - Fator de Impacto em 2010: 2,167 127 - Enzyme kinetics, strutural analysis and molecular modeling studies on a series of Schistosoma mansoni PNP inhibitors (3852) Postigo, M.P., Krogh, R., Terni, M.F., Pereira, H. M., Oliva, G., Castilho, M. S., Andricopulo, A. D.

Journal of Brazilian Chemical Society, 2011, v.22, n.3, P.583-591 - Fator de Impacto em 2010: 1,343

128 - Mesoporous hybrid and nanocomposite thin �ilms. A sol- gel toolbox to create nanocon�ined systems with localized chemical properties (3853)

Soler-Illia, G. J. A. A., Angelomé, P. C., Fuertes, M. C., Calvo, A., Wolosiuk, A., Zelcer, A., Bellino, M. G., Martinez, E. D.

Journal of Sol-Gel Science and Technology, 2011, v.57, n. 3, p.299-312 - Fator de Impacto em 2010: 1,525

135 - Self- structuring of lamellar bridged sisesquioxanes with long side spacers (3866)

Fernandes, M., Nobre, S.S., Qinghon, X., Carcel, C., Cachia, J.N., Cattoen, X., Sousa, J.M., Ferreira, R. A. S., Carlos, L. D., Santilli, C. V., Man, M.W.C., Bermudez, V.Z.

Journal of Physical Chemistry B, 2011, v.115, n.37, p.10877-10891 - Fator de Impacto em 2010: 3,603 136 - SAXS and UV-Vis combined to quick-XAFS monitoring of ZnO nanoparticle formation and growth (3867)

Caetano, B.L., Santilli, C. V., Pulcinelli, S. H., Briois, V.

Phase Transitions, 2011, v.84, n.8, p.714-725 - Fator de Impacto em 2010: 1,006

137 - Thermal behavior of the Cu-22.55 at%Al alloy with small Ag additions (3868)

Silva, R. A. G., Adorno, A. T., Magdalena, A.G., Carvalho, T.M., Stipcich, M., Cuniberti, A., Castro, M.L.

Journal of Thermal Analysis and Calorimetry, 2011, v.103, n.2, p.459-463 - Fator de Impacto em 2010: 1,752

129 - XANES investigation of the enhanced chemical stability of Pd in supported Pd-Mo catalysts (3854)

138 - ß Phase transformations in the Cu-11mass%Al alloy with Ag additions (3869)

130 - Crystallization and preliminary X-ray diffraction studies of BmooPLA2-I, a platelet-aggregation inhibitor and hypotensive phospholipase A2 from Bothrops moojeni venom. (3855)

139 - Exothermic relaxation and endothermic recrystallization of amorphous zirconium tungstate (3870)

Cónsul, J.M.D., Baibich, I.M., Alves, M. C. M.

Catalysis Communications, 2011, v.12, n.14, p.13571360 - Fator de Impacto em 2010: 2,827

Salvador, G. H. M., Marchi-Salvador, D. P., Silveira, L. B., Soares, A. M., Fontes, M. R. M.

Acta Crystallographica F, 2011, v.67, n.8, p.900-902 - Fator de Impacto em 2010: 0,563 131 - Structural basis of importin-a-mediated nuclear transport for Ku70 and Ku80 (3858)

Takeda, A. A. S., Barros, A.C., Chang,C-W, Kobe, B., Fontes, M. R. M.

Journal of Molecular Biology, 2011, v.412, n.2, p.226234 - Fator de Impacto em 2010: 4,008

132 - In Situ X-ray Absorption Study of the Genesis and Nature of the Reduced Gallium Species in Ga/HZSM5 Catalysts (3859) Faro Jr., A. C., Rodrigues, V. O., Eon, J. G.

Journal of Physical Chemistry C, 2011, v.115, n.11, p.4749-4756 - Fator de Impacto em 2010: 4,52

133 - Electrochemical sensing platform based on polyelectrolyte-surfactant supramolecular assemblies incorporating carbon nanotubes. (3860)

Cortez, M.L., Ceolín, M. R., Azzaroni, O., Battaglini, F.

Analytical Chemistry, 2011, v.83, n.20, p.8011-8018 - Fator de Impacto em 2010: 5,874

134 - Thermoreversible formation and negative thermal expansion of supramacromolecular assemblies of unimolecular micelles in solution (3861) Picco, A., Yameen, B., Azzaroni, O., Ceolín, M. R.

Chemical Communications, 2011, v.47, n.13, p.38023804 - Fator de Impacto em 2010: 5,787 136 | ACTIVITY REPORT 2011

Magdalena, A.G., Adorno, A. T., Carvalho, T.M., Silva, R. A.

Journal of Thermal Analysis and Calorimetry, 2011, v.106, n.339-342 - Fator de Impacto em 2010: 1,752

Ramos, G.R., Catafesta, J., Zorzi, J. E., Jornada, J. A. H., Perottoni, C. A.

Physical Review B, 2011, v.84, n.9, 094121-1-6 - Fator de Impacto em 2010: 3,772

140 - Antimony desinsertion reaction from SbxCoSb3-x (3871)

Miotto, F., Figuêiredo, C.A., Ramos, G.R., Amorin, C. L. G., Gallas, M. R., Perottoni, C. A.

Journal of Applied Physics, 2011, v.110, n.4, p.043529-35 - Fator de Impacto em 2010: 2,064

141 - Synchrotron radiation X-ray micro�luorescence reveals polarized distribution of atomic elements during differentiation of pluripotent stem cells (3872)

Cardoso, S. C., Stelling, M.P., Paulsen, B.S., Rehen, S.K.

PloS One, 2011, v.6, n.12, n.e29244-1-10 - Fator de Impacto em 2010: 4,411

142 - Pre-cancerous changes in urothelial endocytic vesicle leakage, fatty acid composition, and As and associated element concentrations after arsenic exposure (3873) Grasso, E.J., Bongiovanni, G. A., Pérez, R. D., Calderón, R.O.

Toxicology, 2011, v.284, n.1-3, p.26-33 - Fator de Impacto em 2010: 3,641 143 - Bio-inspired algorithms applied to molecular docking simulations (3874) Herbelé, G., de Azevedo Jr., W. F.

Current Medicinal Chemistry, 2011, v.8, n.9, p.13391352 - Fator de Impacto em 2010: 4,63


ARTICLES PUBLISHED IN INDEXED JOURNALS

144 - Protein targets for development of drugs against Mycobacterium tuberculosis (3875) de Azevedo Jr., W. F.

Current Medicinal Chemistry, 2011, v.18, n.9, p.1255-1257 - Fator de Impacto em 2010: 4,63 145 - Molecular dynamics simulations of protein targets identi�i�ied in Mycobacterium tuberculosis (3876)

de Azevedo Jr., W. F.

Current Medicinal Chemistry, 2011, v.18, n.9, p.1255-1527 - Fator de Impacto em 2010: 4,63 146 - Highly oriented VO2 thin �ilms prepared by electrodeposition (3882)

Cezar, A. B., Graff, I. L., Rikers, Y., Schreiner, W. H., Mattoso, N.

Electrochemical and Solid State Letters, 2011, v. 14, n. 3, p. D23-D25 - Fator de Impacto em 2010: 1,967

147 - Photoabsorption and desorption studies on thiophene- based polymers following S K-shell excitation (3886) Wender, H., Santa Rita, J. R., Migowski, P., Arantes, C., Feil, A. F., Aráujo, G., Roman, L. S., Oliveira, L. F. de, Micaroni, L., Prechtl, M. H. G., Leal, J., Rocco, M. L. M., Machado, G., Dupont, J.

Journal of Electron Spectroscopy and Related Phenomena, 2011, v.184, n.3-6, n.265-269 - Fator de Impacto em 2010: 1,75 148 - Spectroscopic study of the polymerization of intercalated anilinium ions in different montmorillonite clays (3893) Nascimento, G. M. do, Temperini, M. L. A.

Journal of Molecular Biology, 2011, v. 1002, n. 1-3, p. 63-69 - Fator de Impacto em 2010: 4,008 149 - Size-controllable synthesis of functional heterostructured TiO(2)-WO(3) core-shell nanoparticles (3902) Santos, E. B., Silva, J.M.S., Sigoli, F. A., Mazali, I. O.

Journal of Nanoparticle Research, 2011, v.13, n. 11, p.5909-5917 - Fator de Impacto em 2010: 3,25

150 - Mass spectrometry and X-ray diffraction analysis of two crystal types of Dioclea virgata lectin: an antinociceptive protein candidate to structure/function analysis (3909)

Delatorre, P., Rocha, B. A. M., Simões, R. C., Pereira-Júnior, F. N., Silva, H. C., Bezerra, E. H. S., Bezerra, M. J. B., Marinho, E. S., Gadelha, C. A. de A., Santi-Gadelha, T., Farias, D. L., Assreuy, A. M. S., Marques-Domingos, G. F. O., Nagano, C. S., Cavada, B. S.

Applied Biochemistry and Biotechnology, 2011, v. 164, n. 6, p. 741-754 - Fator de Impacto em 2010: 1,879

151 - Quantitative phase analyses through the Rietveld method with X-ray powder diffraction data of heattreated carbamazepine form III (3910)

152 - Crystal structure of propylthiouracil determined using high-resolution synchrotron X-ray powder diffraction (3911) Ferreira, F. F., Trindade, A.C., Antonio, S. G., Paiva-Santos, C. O.

CrystEngComm, 2011, v.13, n.17, p.5474-5479 - Fator de Impacto em 2010: 4,006 153 - Central domain deletions affect the SAXS solution structure and function of Yeast Hsp40 proteins Sis1 and Ydj1 (3914)

Silva, J. C., Borges, J. C., Cyr, D. M., Ramos, C. H. I., Torriani, I.

BMC Structural Biology, 2011, v.11, p. 40-1-13 - Fator de Impacto em 2010: 2,258

154 - Electronic and crystallographic structure, hard X-ray photoemission, and mechanical and transport properties of the half-metallic Heusler compound Co2MnGe (3915) Ouardi, S., Fecher, G. H., Balke, B., Beleanu, A., Kozina, X., Stryganyuk, G., Felser, C., Klob, W., Schrader, H., Bernardi, F., Morais, J. de, Ikenaga, E., Yamashita, Y., Ueda, S., Kobayashi, K.

Physical Review B, 2011, v.84, n. 15, 155122-11 Fator de Impacto em 2010: 3,772

155 - Analysis of liquid crystalline nanoparticles by small angle X-ray diffraction: evaluation of drug and pharmaceutical additives in�luence on the internal structure (3917) Rossetti, F.C., Fantini, M. C. A., Carollo, A.R.H., Tedesco, A. C., Bentley, M. V. L. B.

Journal of Pharmaceutical Sciences, 2011, v.100, n.7, p.2849-2857 - Fator de Impacto em 2010: 3,031

156 - Crystallization and preliminary structural analysis of the giant haemoglobin from Glossoscolex paulistus at 3.2A (3918)

Bachega, J.F.R., Bleicher, L., Horjales, E.R., Santiago, P. S., Garratt, R. C., Tabak, M.

Journal of Synchrotron Radiation, 2011, v.18, n.1, p.24-28 - Fator de Impacto em 2010: 2,335 157 - In Situ X-ray Absorption Study of the Genesis and Nature of the Reduced Gallium Species in Ga/HZSM5 Catalysts07/12/2 (3919) Faro Jr., A. C., Rodrigues, V. O., Eon, J. G.

Journal of Physical Chemistry C, 2011, v.115, n.10, p.4749-4756 - Fator de Impacto em 2010: 4,52

158 - Analysis of metal concentration levels in water, sediment and �ish tissues from Toledo municipal lake by applying SR-TXRF technique (3925)

Espinoza-Quiñones, F. R., Módenes, A. N., Palácio, S. M., Lorenz, E. K., Oliveira, A. P.

Water Science & Technology, 2011, v.63, n.7, p.15061512 - Fator de Impacto em 2010: 1,056

Antonio, S. G., Benini, F. R., Rosa, P. C. P., Ferreira, F. F., PaivaSantos, C. O.

159 - Mesoporous Pt and Pt/Ru alloy electrocalysts for methanol oxidation (3927)

Journal of Pharmaceutical Sciences, 2011, v.100, n.7, p.2658-2664 - Fator de Impacto em 2010: 3,031

Journal of Power Sources, 2011, v. 196, n., p. 17231729 - Fator de Impacto em 2010: 4,283

Franceschini, E. A., Planes, G. A., Williams, F. J., Soler-Illia, G. J. A. A., Corti, H. R.

Brazilian Synchrotron Light Laboratory | 137


ARTICLES PUBLISHED IN INDEXED JOURNALS

160 - Structure and morphology of spinel MFe2O4 (M=Fe, Co, Ni) nanoparticles chemically synthesized from heterometallic complexes (3954)

167 - Uniaxial compression and stretching deformation of an i-PP/EPDM/organoclay nanocomposite (3966)

Journal of Colloid and Interface Science, 2011, v.358, n.1, p.39-46 - Fator de Impacto em 2010: 3,066

Polymer, 2011, v.52, n.4, p.1037-1044 - Fator de Impacto em 2010: 3,794

Guerra, M.B.B., Schaefer, C.E.G.R., Rosa, P.F., Simas, F.N.B., Pereira, T.T.C., Pereira Filho, E.R.

168 - Self-organized TiO2 nanotube arrays: synthesis by anodization in an ionic liquid and assessment of photocatalytic properties (3967)

Water Air Soil Pollut, 2011, v.222, n.1-4, p.91-102 Fator de Impacto em 2010: 1,765

Wender, H., Feil, A. F., Diaz, L.B., Ribeiro, C.S., Machado, G. J., Migowski, P., Weibel, D. E., Dupont, J., Teixeira, S. R.

ACS Applied Materials & Interfaces, 2011, v.3, n.4, p.1359-1365 - Fator de Impacto em 2010: 2,925

Naidek, K.P., Bianconi, F., Rocha, T. C. R., Zanchet, D., Bonacin, J.A., Novak, M. A., Vaz, M. G. F., Winnischofer, H.

161 - Heavy Metals Contamination in Century-Old Manmade Technosols of Hope Bay, Antarctic Peninsula (3955)

162 - Photostability of amino acids to Lyman a radiation: Glycine (3956) Ferreira-Rodrigues, A. M., Homem, M. G. P., Naves de Brito, A., Ponciano, C. R., Silveira, E. F. da

International Journal of Mass Spectrometry, 2011, v.306, n.1, p.77-81 - Fator de Impacto em 2010: 2,009

163 - Crystallization and characterization of an in�lammatory lectin puri�ied from the seeds of Dioclea wilsonii (3960)

Rangel, T.B.A., Assreuy, A. M. S., Pires, A. F., Carvalho, A.U., Benevides, R. G., Simões, R. C., Silva, H. C., Bezerra, M. J. B., Nascimento, A. S. F., Nascimento, K. S., Nagano, C. S., Sampaio, A. H., Delatorre, P., Rocha, B. A. M., Fernandes, P. M. B., Cavada, B. S.

Molecules, 2011, v. 16, n. 6, p.5087-5103 - Fator de Impacto em 2010: 1,988

164 - Puri�ication and partial characterization of a new pro-in�lammatory lectin from Bauhinia bauhinioides Mart (Caesalpinoideae) seeds (3961) Silva, H. C., Bari, A.F., Pereira-Júnior, F. N., Simões, R. C., Barroso-Neto, I.L., Nobre, C.B., Pereira, M.G., Nascimento, K. S., Rocha, B. A. M., Delatorre, P., Nagano, C. S., Assreuy, A. M. S., Cavada, B. S.

Protein and Peptide Letters, 2011, v.18, n.4, p.396402 - Fator de Impacto em 2010: 1,849 165 - Structural analysis of ConBr reveals molecular correlation between the carbohydrate recognition domain and endothelial NO synthase activation (3962)

Bezerra, E. H. S., Rocha, B. A. M., Nagano, C. S., Bezerra, G. A., Moura, T. R., Bezerra, M. J. B., Benevides, R. G., Sampaio, A. H., Assreuy, A. M. S., Delatorre, P., Cavada, B. S.

B i o c h e m i c a l a n d B i o p hys i c a l Re s e a rc h Communications, 2011, v.408, n.4, p.566-570 - Fator de Impacto em 2010: 2,595

166 - Tracking defect type and strain relaxation in patterned Ge/Si(001) islands by X-ray forbidden re�lection analysis (3963)

Richard, M. I., Malachias, A., Rouvière, J.-L., Yoon, T.-S., Holmström, E., Xie, Y.-H., Favre-Nicolin, V., Holÿ, V., Nordlund, K., Renaud, G., Metzger, T.-H.

Physical Review B, 2011, v. 84, n. 7, 075314-1-7 Fator de Impacto em 2010: 3,772 138 | ACTIVITY REPORT 2011

Thompson, A., Bianchi, O., Amorin, C. L. G., Lemos, C., Teixeira, S. R., Samios, D., Giacomelli, C., Crespo, J. S., Machado, G.

169 - On the formation of anisotropic gold nanoparticles by sputtering onto a nitrile functionalised ionic liquid (3970)

Wender, H., Migowski, P., Feil, A. F., Oliveira, L. F. de, Prechtl, M. H. G., Leal, R., Machado, G., Teixeira, S. R., Dupont, J.

Physical Chemistry Chemical Physics (PCCP), 2011, v.13, n.30, p.13552-13557 - Fator de Impacto em 2010: 3,453 170 - Comparative survival analysis of deinococcus radiodurans and the haloarchaea natrialba magadii and haloferax volcanii exposed to vacuum ultraviolet irradiation (3971)

Abrevaya, X., Paulino-Lima, I. G., Galante, D., Rodrigues, Fa., Mauas, P. J. D., Cortón, E., Lage, C. A. S.

Astrobiology, 2011, v.11, n.10, p.1034-40 - Fator de Impacto em 2010: 2,369 171 - Lead deposition in bovine enamel during a pHcycling regimen simulating the caries process (3972)

Molina, G. F., Costa Almeida, G. R., Souza- Guerra, C., Cury, J. A., Barroso, R. C., Gerlach, R. F.

Caries Research, 2011, v.45, n.5 , p.469-474 - Fator de Impacto em 2010: 2,926 172 - Optical properties of polydisperse submicrometer aggregates of sulfur-containing zinc oxide consisting of spherical nanocrystallites (3974) Bosshard, G., Silva, J.M.S., Lima, S. A. M., Mazali, I. O., Sigoli, F. A.

New Journal of Chemistry, 2011, v. 35, n.4, p.902908 - Fator de Impacto em 2010: 2,631 173 - Fibrinogen stability under surfactant interaction (3985) Hassan, N., Barbosa, L. R. S., Itri, R., Ruso, J. N.

Journal of Colloid and Interface Science, 2011, v.362, n.1, p.118-126 - Fator de Impacto em 2010: 3,066

174 - Particle size control of Y2O3:Eu3+ prepared via a coconut water-assisted sol-gel-method (3990) Gomes, M. de A., Valerio, M. E. G., Macedo, Z. S.

Journal of Nanomaterials, 2011, v. 2011, p. 1-6 - Fator de Impacto em 2010: 1,656


ARTICLES PUBLISHED IN INDEXED JOURNALS

175 Radioluminescence properties of decaoctahedral BaZrO3 (3991) Moreira, M. L., Volanti, D. P., Andrés, J., Montes, P. J. R., Valerio, M. E. G., Varela, J. A., Longo, E.

183 - Parametric study of the gel-combustion synthesis of nanocrystalline ZrO2-based powders (4032)

176 - Aharonov-Bohm-Casher problem with a nonminimal Lorentz-violating coupling (3992)

184 - Thermal evolution of Pt-Rich FePt/Fe3O4 heterodimers studied using X-ray absorption near-edge spectroscopy (4033)

Scripta Materialia, 2011, v.64, n.2, p. 118-121 - Fator de Impacto em 2010: 2,806 Belich, H., Silva, E. O., Ferreira, M. M., Orlando, M. T. D.

Physical Review D: Particles, �ields, gravitation and cosmol, 2011, v. 83, n. 2 p. 125025-1-8 - Fator de Impacto em 2010: 4,964 177 - Noncommutative �luid dynamics in the Kähler parametrization (3993) Holender, L., Santos, M. A., Orlando, M. T. D., Vancea, I. V.

Journal of Sol-Gel Science and Technology, 2011, v. 84, n. 10 , p. 105024-31 - Fator de Impacto em 2010: 1,525 178 - Waterborne polyurethane/acrylate: comparison of hybrid and blend systems (3995)

Peruzzo, P. J., Anbinder, P. S., Pardini, O. R., Vega, J., Costa, C. A., Galembeck, F., Amalvy, J. I.

Progress in Organic Coatings, 2011, v. 72, n. 3, p. 429- 437 - Fator de Impacto em 2010: 1,862 179 - XRD analysis of human dental tissues using synchrotron radiation (4008) Colaço, M. V., Barroso, R. C., Porto, I. M., Gerlach, R. F., Costa, F. N., Braz, D., Droppa Jr., R.

Acta Crystallographica A, 2011, v. A67, p. C484 - Fator de Impacto em 2010: 54,332 180 - Fragmentation of the CH2Cl2 molecule by proton impact and VUV photons (4028)

Alcantara, K. F., Wolff, W., Gomes, A. H. A., Sigaud, L., Soriano, S., Oliveira, V., Rocha, A. B., Santos, A. C. F.

Journal of Physics B, 2011, v. 44, n. 16, p. 165205-19 - Fator de Impacto em 2010: 1,902 181 - Photodissociation of methyl formate in circumstellar environment: stability under soft X-rays (4029)

Fantuzzi, F., Pilling, S., Santos, A. C. F., Baptista, L., Rocha, A. B., Boechat-Roberty, H. M.

Monthly Notices of the Royal Astronomical Society, 2011, v. 417, n. 4, p. 2631-2641 - Fator de Impacto em 2010: 4,888

182 - Formation routes of interstellar glycine involving carboxylic acids: possible favoritism between gas and solid phase (4030) Pilling, S., Baptista, L., Boechat-Roberty, H. M. , Andrade, D. P. P.

Astrobiology, 2011, v. 11, n. 9, p. 883-893 - Fator de Impacto em 2010: 2,369

Fábregas, I. O., Lamas, D. G.

Powder Technology, 2011, v. 214, n.2, p. 218-228 Fator de Impacto em 2010: 1,887 Figueroa, S. J. A., Stewart, S. J., Rueda, T., Hernando, A., de la Presa, P.

Journal of Physical Chemistry C, 2011, v. 115, n. 13, p. 5500-5508 - Fator de Impacto em 2010: 4,52 185 - Manipulation of molecular transport into mesoporous silica thin �ilms by the in�iltration of polyelectrolytes (4039)

Brunsen, A., Calvo, A., Williams, F. J., Soler-Illia, G. J. A. A., Azzaroni, O.

Langmuir, 2011, v. 27, n. 8, p. 4328-4333 - Fator de Impacto em 2010: 4,268 186 - Modulation of the phamacological activities of secretory phospholipase A2 from Crotalus durissus cascavella induced by naringin (4073)

Santos, M. L., Toyama, D. O., Oliveira, S. C. B., Cotrim, C. A., Diz-Filho, E. B. S., Fagundes, F. H. R., Soares Jr., P. C., Aparicio, R., Toyama, M. H.

Macromolecules, 2011, v. 16, p. 738-766 - Fator de Impacto em 2010: 4,837 187 - Measurement of L X-ray �luorescence cross-section for elements with 45<= Z <= 50 using synchrotron radiation at 8 KeV (4103) Bonzi, E., Badiger, N. M., Grad, G. B., Barrea, R. A., Figueroa, R.

Nuclear Instr and Meth in Physics Research B, 2012, v. 269, n. , p. 2084-2089 - Fator de Impacto em 2010: 1,042 188 - Structure and behavior of human alpha-thrombin upon ligand recognition: thermodynamic and molecular dynamics studies (4117)

Silva, V. de A., Cargnelutti, M. T., Giesel, G. M., Palmieri, L. de C., Monteiro, R. Q., Verli, H., Lima, L. M. T. R.

PloS One, 2011, v. 6, n. 9, p. e24735-1-12 - Fator de Impacto em 2010: 4,411 189 - Using speciation diagrams to improve synthesis of magnetic nanosorbents for environmental applications (4229) Campos, A. F. C., Aquino, R., Cotta, T. A. P. G., Tourinho, F. A., Depeyrot, J.

190 - Investigation of mineral distribution in bone by synchrotron X-ray �luorescence microscopy after therapy (4241) Lima, I., Carvalho, A. C. B., Henriques, H. N., Sales, E., Granjeiro, J. M., Guzmán-Silva, M. A., Lopes, R. T.

Brazilian Synchrotron Light Laboratory | 139


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Activity Report 2011

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