POSTER ABSTRACTS 21
ʺReactivity Studies of o-Benzynes Toward Nucleic Acid Components Using The Distonic Ion Approach and FT-ICRʺ Karinna Campbell*, John J. Nash and Hilkka I. Kenttämaa Purdue University, Department of Chemistry, West Lafayette, IN 47907
Abstract σ,σ-Biradicals have been discovered to be the biologically reactive intermediates of the enediyne antitumor drugs responsible for DNA cleavage in cancer cells. Understanding the parameters that control the reactivity of these biradicals is likely to lead to the synthesis of better nonhydrolytic DNA cleaving drugs. The magnitude of the singlet-triplet (S-T) gap of a biradical, which is defined as the energy difference between the lowest-energy singlet and triplet states, depends on the extent of the interaction between the radical orbitals. A large S-T gap is indicative of strong coupling between the radical centers. The orthobenzyne has a large S-T gap (-37.5 kcal/mol) and is best thought of as an activated alkyne rather than a biradical. This is evident in the reactivity observed for o-benzyne – nucleophilic or electrophlilic addition reactions (e.g. Diels-Alder reactions). Though the o-benzyne is the most widely studied of the three simplest aryne isomers, its reactivity toward DNA components has not been explored. We employ the distonic ion approach to study the intrinsic reactivity of biradicals by using mass spectrometry. We report here a kinetic reactivity study on three charged o-benzynes, 3,4-didehydroisoquinolinium, 5,6-didehydroisoquinolinium and 7,8-didehydroisoquinolinium ions, and comparison of the results to those obtained for other isomeric biradicals. Quinoline and isoquinoline biradical precursors were synthesized according to reported methods and their structures verified by mass spectrometry and nuclear magnetic resonance spectroscopy. The charged didehydroarenes were generated in a 3-T dual cell Finnigan Model FTMS 2001 Fourier-transform ion cyclotron resonance mass spectrometer by dissociation, ion molecule reactions and isolated. Their ionic reaction products and reaction efficiencies were determined for reactions with various DNA components. Exclusive hydrogen atom abstraction was observed for phenyl monoradicals. However, no such reactivity was observed for the 5,6-didehydroisoquinolinium ion. This o-benzyne was found to yield addition/elimination products when reacted with d-ribose.
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ʺStudies of Violet Dye Production by Marine Fungus from Tanzaniaʺ Kia Walcott Abstract
The objective of this experiment was to manipulate the Anthraquinone biosynthesis in marine fungi to produce a cheap and environmentally friendly source of Anthraquinone dye intermediates. The fungus in this study was isolated from the marine sediments of the Dar es Salaam Coast and grown on two microbial media: Malt extract agar /broth and Aquatic Yeast agar/broth. A series of media variations were made to optimized dye production and fungal growth. The pH of each flask was varied, 2 flasks per pH level (3.5, 4.5, 5.5, 6.5). For the media variations, three different types of media were employed: Malt Extract Broth, Aquatic Yeast Broth, and Czapeck Broth. Carbohydrate variation within the media was performed using Aquatic Yeast broth. Instead 1% of a given sugar, the sugar concentration was increased to 2% and in addition to Glucose, 2% Fructose, Inulin, Starch, and Lactose were substituted. A time course of dye production was taken using a spectrophotometer to test the absorbency the pH 6.5 media and its contents at
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