Synchrotron X-radiation protein crystallography: instrumentation, methods and applications

This review describes the utilisation of synchrotron X-radiation (SR) in protein crystallography. For the general reader a brief discussion is given of the basics of protein structure analysis including an outline of the problems of sample radiation damage, the inherent weakness of individual reflections and the large amounts of data that need to be collected as well as the 'phase problem' of crystallography. The properties of synchrotron radiation emitted by relativistic electrons in simple circular orbits in bending magnets and by more sophisticated electron motions induced in wiggler or undulator magnets are discussed. The impact of newer high brightness synchrotron radiation sources in protein crystallography is assessed. The instrumentation required to monochromatise and focus the radiation onto typically small protein crystal samples and to detect the diffraction pattern is described. Both step scanning and energy dispersive techniques to optimise anomalous dispersion are covered. A gazetteer is given of the instruments providing data collection facilities for protein crystallography which are available on SR sources around the world. The modifications that are needed to standard data processing techniques are dealt with, taking account, for instance, of the position, angle and wavelength correlatable properties of photons incident to a sample from an SR source; properties which affect reflection prediction in both camera or diffractometer work.