Sources, instrumentation and detectors for protein crystallography

Some of the requirements for protein crystallography experiments on a synchrotron are described. Although data from different types of crystal are often collected without changing the X-ray beam properties, there are benefits if the incident beam is matched to a particular crystal and its diffraction pattern. These benefits are described with some examples. Radiation damage and other effects impose limits on the dose and dose rate on a protein crystal if the maximum amount of data is to be obtained. These limitations have possible consequences for the X-ray source required. Presently available commercial detector systems provide excellent data for protein crystallography but do not quite reach the specifications of the “ideal” detector. In order to collect the most accurate data (e.g. for very weak anomalous scattering applications) detectors that produce near photon counting statistics over a wide dynamic range are required. It is possible that developments in “pixel” detectors will allow these demanding experiments to be carried out more easily. Finally some possible applications of X-ray free electron lasers for biological applications are discussed.