Macromolecular crystallography with synchrotron radiation. II. Results

Crystallographic data for three different protein crystals (glycogen phosphorylase b to 2 Å resolution, β-lactamase I to 2.5 Å resolution and troponin C to 6 Å 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 ( × 125) 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.