RADIATION DAMAGE STUDIES OF PROTEIN CRYSTALS

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。 辐射损伤是异常色散相移实验的一个严重问题，因为在MAD或SAD实验中，样品在感兴趣的典型波长处的吸收增加。结果发现，在纽纽林的情况下，在吸收边拐点的数据采集和10度楔形的远距离波长允许结构解，而常规的三波长MAD实验和最大能量下的SAD是无效的。随后对不同蛋白质进行的实验表明，双波长MAD(使用小的振荡楔形)确实可能是新结构相变的最佳策略。为了用另一个案例证实这一结果，对鸡纽蛋白晶体(尾部碎片)进行了实验：从几个晶体连续收集MAD和SAD数据，直到出现实质性的衍射损伤(在高分辨率下观察到衍射点的大幅减少)。随着晶体吸收总剂量的增加，晶相的质量下降，硒和硫位的衰变增加。正如在其他情况下发现的那样，双波长MAD图的质量略好于SAD对应图。

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. Subsequent experiments on different proteins hinted that two-wavelength MAD (using small oscillation wedges can indeed be the optimal strategy for phasing structures the novo. To confirm this result with one more case, an experiment was carried out on crystals of chicken Vinculin (tail fragment): Successive MAD and SAD data collections were carried from several crystals until substantial diffraction damage (substantial decrease of diffraction spots at high resolution was observed). The quality of the phases decreased, and the Selenium and Sulphur site decay increased as the total dose absorbed by the crystals increased. Two-wavelength MAD maps were of slightly better quality than the SAD counterparts, as found for other cases.