Crystallography

SCIENCE

“ The rise of crystallography has paved the way to understanding atomic structure and bonding”

Here X-ray diffraction crystallography is used to study the molecular structure of the enzyme methanol dehydrogenase

DID YOU KNOW?

Von Laue was asked by the Nazis to work on a nuclear weapons programme, but he refused

Crystals under the microscope

2014 is the year of crystallography, but what is it?

Crystallography is the analysis of crystals, used to increase our understanding of internal atomic structures – not just of minerals but of any substance which can be crystallised.

The practice is centred on the unique geometry of a crystal. First theorised by French physicist Auguste Bravais, all of a substance’s angles are measured to fi nd a crystal or lattice system. Co-ordinates are plotted to determine any symmetry, which can then defi ne the atomic structure.

X-ray crystallography was popularised by German physicist Max von Laue in 1912, who showed crystals could be diffracted by this method. Atoms within the crystal diffract the X-rays and the angles of the defl ection are measured. Scientists can then map a material’s inner structure in great detail.

This technique can be used to determine the structure of organic substances such as proteins and DNA, as well as vitamins, alloys and other composite materials.

The rise of crystallography has paved the way to understanding atomic structure and bonding across many scientifi c fi elds like never before, though this technique remains relatively unknown. This is why the UN has declared 2014 as the International Year of Crystallography in order to raise its profi le.

The origins of X-ray crystallography

The practice is thought to have originated from the work of Max von Laue. The German physicist worked in universities across the country, under the guidance of famous scientists Max Planck and Albert Einstein. He discovered the diffraction of X-rays through the atoms of a crystal in 1912. His results were developed with the help of physicists Paul Knipping and Walter Friedrich and demonstrated the period arrays of atoms in crystals.

Englishman William Bragg and his son Lawrence built on Von Laue’s work to create an X-ray spectrometer that analysed the molecular structure of crystals, showing the relative positions of atoms in crystals. Von Laue and the Braggs received the Nobel Prize for Physics in 1914 and 1915, respectively.

Mapping out a protein

How crystallography unlocks our microbiology 2. Protein crystal

A protein is too small to analyse in its natural state so it is concentrated and grown into a crystal form.

1. X-rays

An X-ray machine provides high-frequency EM radiation which diffracts on contact with the crystal.

6. Protein model

From the computer imagery and electron density map, a model can be created that displays the protein’s atomic structure.

3. Catching some rays

A detector measures the properties of the rays and how they’re distorted.

4. Make an image

The data is then uploaded to a computer so crystallographers can examine the crystal’s molecular structure.

5. Electron density map

Atomic co-ordinates are drawn up and a high-resolution map is created showing the newfound diffraction pattern.