STRATEGY CALCULATION FOR PHASING PROTEIN CRYSTAL STRUCTURES IN THE PRESENCE OF R

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 尽管有证据表明选择用于数据收集的能量对数据的全球质量没有太大影响[Shimizu，Hirata，Hasegawa，Ueno&Yamamoto(2007)J.同步辐射。14 4-10]，不同能量下的局部辐射损伤效应还没有得到充分的研究。实验研究了9 keV和14.5 keV的二硫键对HWL溶菌酶的还原速率。二硫键的损伤发生相对较快，易于观察和量化，辐射损伤机理与其他元素相同。来自不同晶体的测量表明，二硫化物桥的单位剂量减少的速度与地点有关，暴露的地点越多，衰变速度就越快。对数据的仔细分析表明，在能量较高的情况下，每个剂量单位的部位衰变总体上略快一些。对来自甲氧基鞭毛杆菌的Se-Met取代的核苷酸结合蛋白重复实验。在更高的能量下，Se-Met的衰变速度也更快，但在这种情况下，趋势并不那么明显，可以归因于数据中的噪音。这些结果指出了晶体衍射实验中剂量计算方法的缺陷，并为未来的发展提供了途径。

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. Although there is evidence that the energy chosen for data collection does not have a great deal of effect in the global quality of the data [Shimizu, Hirata, Hasegawa, Ueno & Yamamoto (2007) J. Synchrotron Radiat. 14 4-10], the effects of local radiation damage at different energies have not been sufficiently studied. Experiments were undertaken to study the reduction rate of disulfide bridges at 9 and 14.5 keV on HEWL lysozyme. The damage to disulfide bridges happens relatively quickly and it is easy to observe and quantify, and the radiation damage mechanism is thought to be the same as for other elements. Measurements from different crystals indicate that the rate of reduction per dose unit of the disulfide bridges is site depending, with more exposed sites showing an increased rate of decay. Careful analysis of the data suggest that the site decay per dose unit is overall slightly faster at the higher energy. The experiment was repeated for a Se-MET substituted nucleotide binding protein from methylobacillus Flagellatus. The decay for the Se-MET sites also appears faster at higher energy, but in this case the trend was not so clear and could be attributed to noise in the data. These results point to a flaw in the way dose is calculated for crystal diffraction experiments and provide the path for future developments.