THE USE OF A WIDE-BANDPASS BEAM IN MACROMOLECULAR CRYSTALLOGRAPHY

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 多层技术可用于提供宽带通X射线束，其通量通常比来自Si（111）晶体的单色束高约30倍，其通常用于大分子晶体学束线。 作为提高数据吞吐量和时间分辨研究潜力的研究的一部分，BL 4 -2上安装的多层光学器件用于收集肌红蛋白晶体的单晶衍射数据。 为了进行适当的比较，首先用Si（111）单色器测量数据，然后用多层光学器件测量数据，保持其他参数固定。 以每帧0.5度和5秒的曝光时间收集完整的数据集（总共69.5度）。 来自多层膜的数据集衍射至约1.8 A，最终数据集处理至2 A分辨率。 由于在偏移位置使用小面积MarCCD 165探测器，因此数据具有相当低的冗余。收集了大约70度的数据。 多层膜的衍射斑点是条纹状的，特别是在较高的衍射角下，这是由于宽的能带通（约2-3%）。数据处理得很好。最终的统计数据表明93.5%的完整性，冗余度为2.1，Rsym为16.6%。 如果有的话，对细化和电子密度图的影响目前正在进行中，但这些结果已经清楚地表明，多层束可用于快速数据收集，晶体筛选和可能的时间分辨研究。

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.