THE USE OF A WIDE-BANDPASS BEAM IN MACROMOLECULAR CRYSTALLOGRAPHY

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Multilayer technology can be used to provide a wide band-pass x-ray beam, with a flux typically ~30 times higher than monochromatic beam from a Si(111) crystal, which is typically used in macromolecular crystallography beam lines. As a part of a study to pursue increased data throughput as well as the potential for time-resolved studies, the multilayer optics installed on BL4-2 was used to collect single crystal diffraction data from myoglobin protein crystals. To make proper comparison, data were measured first with the Si(111) monochromator and thereafter with the multilayer optic, keeping other parameters fixed. A complete data set (a total of 69.5 degree) was collected with 0.5 degree per frames and an exposure time of 5 sec. The data set from the multilayer diffracted to around 1.8 A and the final data set was processed to 2 A resolution. Since a small-area MarCCD165 detector was used in an offset position, the data had rather low redundancy. Approximately 70 degrees of data were collected. The diffraction spots from the multilayer were streaked, especially at higher diffraction angles, due to the wide energy band-pass (approx 2-3%),. However, the data processed well. The final statistics indicated 93.5% completeness with a redundancy of 2.1 and an Rsym of 16.6%. The effect, if any, on the refinement and electron density map is currently underway, but these results clearly already demonstrate that multilayer beam can be used for rapid data collection, crystal screening and possibly time-resolved studies.