Macromolecular crystallography with synchrotron radiation. II

Crystallographic data for three different protein crystals (glycogen phosphorylase b to 2 A resolution, β-lactamase I to 2.5 A resolution and troponin C to 6 A resolution) have been recorded using the intense synchrotron radiation beam emitted by the DCI storage ring at LURE and the DORIS storage ring at DESY/EMBL. Reduction in exposure times of approximately 50-fold and an increase in crystal lifetime of at least fivefold are observed when data recorded at LURE are compared with those recorded with a conventional rotating-anode source. These factors have made possible data collection which otherwise would have been impossible. For large crystals of phosphorylase b a greater reduction in exposure time (x125) is made possible by the focusing geometry of the synchrotron-monochromator system which allowed irradiation of a larger volume of the crystal (collimator size increased from 0.3 to 1.0 mm) without significant increase in spot overlap on the film. The data processing statistics for phosphorylase b and β-lactamase compare favourably with those from data recorded on a conventional source (improvements in merging R values of between 1 and 4%). For phosphorylase b, but not for β-lactamase or troponin C, significant thermal diffuse scatter is observed on photographs recorded with synchrotron radiation. The possible origin of this phenomenon and its effect on data processing are discussed. (Auth.)