Recent developments in micro-diffraction on protein crystals.

Protein crystallography micro-diffraction and micro small-angle X-ray scattering at a third-generation synchrotron radiation source undulator beamline both require a compromise on beam size and beam divergence. Micro small-angle X-ray scattering requires in addition an as-close-as-possible angular approach to the direct beam, which is mainly limited by the beam divergence at the sample position. Both techniques have been developed at the ESRF microfocus beamline in a complimentary way. The development of a dedicated microgoniometer in the frame of an EMBL/ESRF collaboration has revealed the potential of micro-diffraction for protein crystallography and is a step in the quest for user friendly instrumentation.