Readiness evaluation method for X-ray difraction data collection systems
W. Ding, Z. J. Liu · Acta Crystallographica Section A Foundations of Crystallography · 2011
Sessions C660The handling of cryo-cooled protein crystals has been automated by robotics systems, where samples are kept in liquid-nitrogen storage, to be loaded on the goniometer for the experiment and retrieved afterwards.Crystals are automatically centered in the X-ray beam by means of an automated goniometer head and software that applies algorithms that determine the crystal position in three-dimensional space from images taken with high resolution digital microscopes.For the steps that follow, we report on the development of XPRESSO, a new crystal screening and data collection system for macromolecular samples.The screening process starts out by taking short series of X-ray diffraction images from which the general quality of the crystal is judged by the resolution limit, the mosaicity, the ability to find the unit cell, and the presence of ice rings.User input limits for the unit cell help distinguish between the actual sample and unwanted crystals, such as from buffers or salts co-crystallized with a protein.For the data collection a strategy is determined based on the screening results.It takes into account the exposure time, sample to detector distance, scan width, and resolution limit, among others.The data is integrated in parallel to the data acquisition, followed by data scaling.Space group determination is the final step.Results are provided as HTML reports, including Matthews coefficient probabilities.