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Rosalind Franklin and DNA.osalind Franklin (above right) took theiffraction photograph that led to Watson andricks publication of the helical structure of theform of DNA.

A reconstructed

precession image. Eachpoint of light is interpreted as a

reflection from a plane ofatoms. Thousands of these

reflections are collected and

how bright they are and theangle at which they are

collected is used to determinethe position of the atoms in the

crystal. Reflections furtheraway from the centre (at

higher angle) are used for high-resolution data.

X-RAY CRYSTALLOGRAPHY

X-ray Generators - Different Scales.X-rays can be generated in the laboratory (above right) from the domestic power supply -r, very powerful X-rays of tuneable wavelength, can be generated at synchrotron facilitieske the Diamond Light Source in Harwell, Oxfordshire (above left).

Watson and Crick and theirodel of DNA (above) based onosalind Franklin and Maurice

Wilkins diffraction photographs.

Dorothy Hodgkin and

Insulin.She worked for over 30 years to fully

calculate the structure of insulin(behind) at a time when all thediffraction intensities had to be

determined by hand.

References and CitationsStructures downloaded from th e RSCP Protein Databank. (http://www.rcsb.org/pdb/home/home.do) (from top: b-DNA, hens egg lysozyme, HIV reverse transcriptase, pig insulin).b-DNA, lysozyme and reverse transcriptase rendered using Qutemol (M Tarini, P Cignoni, C Montani, IEEE Transactions on Visualization and Computer Graphics, 12 , 5, 1237-1244 , 2006.)Pig insulin rendered using PyMol (The PyMOL Molecular Graphics System, Version 1.5.0.4 Schrdinger, LLC.) Portrait photographs copyright of Sciencephotolibrary and Life Science Foundationhttp://www.lifesciencesfoundation.org). All used without permission. Bruker Microstar photograph copyright Mairi Haddow, University of Bristol. Photograph of Diamond Light Source copyright

of that organisation.

JD Bernal and Kathleen Lonsdale.Lonsdale confirmed the structure of benzene using

X-ray diffraction. Bernal, among other things,worked on Tobacco Mosaic Virus.

Father and son, the Braggs,worked together to develop Braggs Law- the fundamental equation in X-ray

crystallography.

X-rays were discovered in 1895 and are part of the electromagnetic spectrum

like visible light. Like all light they have a wavelength and frequency. Their

wavelength is about the same distance as the space between atoms in solids.

When X-rays pass through a crystal - the X-rays form a diffraction pattern.

nalysing the diffraction pattern using computers allows us to reconstruct the

D structure of the crystal. Knowing the structure of molecules is vital to our

nderstanding of structure and function and has revolutionised fields as diverses medicine and electronics. Crystals of lysozyme.

The first enzyme to have its structuredetermined. Lysozyme crystals show beautiful

symmetry. Lysozyme is important in our defenceagainst bacteria.

The structure of HIV

reverse transcriptase.This is used toconvert RNA into DNAwithin infected cells. Understanding itsstructure allows scientists to develop

drugs to treat disease.

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