RADIATION DAMAGE AS A FUNCTION OF WAVELENGTH

该子项目是利用NIH/NCRR资助的中心赠款提供的资源的许多研究子项目之一。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。所列机构为中心机构，不一定为研究者机构。辐射损伤是异常色散定相实验的一个严重问题，因为在MAD或SAD实验的典型感兴趣波长处样品的吸收增加。已经发现，在粘着斑蛋白的情况下，在吸收边缘拐点和10度楔形中的远程波长处的数据收集允许结构解，其中常规的三波长MAD实验和最大f <$能量处的SAD失败。进行实验以确定a）上述结果是否对其他蛋白质有效，以及B）在这种情况下促进结构解的关键因素是什么：在楔形中的所有波长处同时收集数据，或者避免在最大f“波长处收集数据。对来自根癌土壤杆菌的假定蛋白质（NP_356412. 1）和来自鼠伤寒沙门氏菌的假定葡糖胺-果糖-6-磷酸氨基转移酶（16423107）的晶体进行了实验：从几个晶体中收集连续的MAD和SAD实验，直到出现实质性衍射损伤（观察到高分辨率下衍射斑点的实质性减少）。随着晶体吸收的总剂量的增加，相的质量稳步下降。在双波长MAD实验的情况下，只要数据是以楔形收集的，电子密度图在受到大量辐射损伤后仍然可以解释。然而，当连续收集两个波长时，结构溶液在较低的总吸收剂量下失效

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. Radiation damage is a serious concern for Anomalous Dispersion phasing experiments because of the increased absorption by the sample at the typical wavelength of interest for MAD or SAD experiments. It has been found that data collection at the absorption edge inflection point and the remote wavelength in 10 degrees wedges allowed structure solution in the case of vinculin, where conventional three-wavelength MAD experiments and SAD at the maximum f¿¿ energy failed. Experiments were carried out to determine a) if the above results are valid for other proteins and b) what is the critical factor which facilitates structure solution in such cases: simultaneous data collection at all wavelengths in wedges, or avoiding data collection at the maximum f'' wavelength. The experiments were carried out on crystals of the hypothetical protein (NP_356412.1) from Agrobacterium tumefaciens and a putative glucosamine-fructose-6-phosphate aminotransferase (16423107) from Salmonella typhimurium: Successive MAD and SAD experiments were collected from several crystals until substantial diffraction damage (substantial decrease of diffraction spots at high resolution was observed. The quality of the phases decreased steadily as the total dose absorbed by the crystals increased. In the case of two-wavelength MAD experiments the electron density maps could still be interpreted after substantial radiation damage as long as the data were collected in wedges. However, when the two wavelengths were collected consecutively, structure solution failed at a lower total absorbed do