S K-EDGE XAS STUDIES AS A PROBE OF ELECTRONIC STRUCTURE/CONTRIBUTION TO FUNCTION

这个子项目是许多利用资源的研究子项目之一 由NIH/NCRR资助的中心拨款提供。子项目的主要支持 而子项目的主要调查员可能是由其他来源提供的， 包括其它NIH来源。 列出的子项目总成本可能 代表子项目使用的中心基础设施的估计数量， 而不是由NCRR赠款提供给子项目或子项目工作人员的直接资金。 配体K边XAS提供了配体金属键合的直接探针。我们已经开发了这种方法来研究模型复合物和蛋白质活性位点的一些集群和网站，特别是Fe-S，Cu-S集群和二硫杂环戊烯含Mo/W网站的电子结构。在之前的提案期间，在几项研究中，我们评估了HiPIP和铁氧还蛋白之间差异的一般性，并使用表征良好的模型复合物和蛋白质系统地研究了氢键，溶剂相互作用以及改变这些和其他簇周围的介电场的影响，并将实验结果与DFT计算相结合。 我们还开发了键合/几何结构的相关性在钼（三）二硫烯和氧代transnsfer的DMSO还原酶家族的酶和模型的机制。 在本研究中，我们计划扩展这一方法，并将其与互补光谱学联合收割机相结合，来研究几种Fe-S系统，如SAM与丙酮酸裂解酶激活酶中Fe_4S_4簇的相互作用; MutY -一种来自大肠杆菌的DNA糖基化酶; Fe_2S_2蛋白结合？9去饱和酶;以及Cys->Ser突变对铁硫簇合物中电子离域的影响。 我们还打算研究一系列钼单-和双-氧代双（二硫杂环戊烯）配合物，模型的亚硫酸盐氧化酶家族的状态。 具体目标是定义酶和模型复合物的电子结构，并了解酶反应的结构和功能之间的相关性。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Ligand K-edge XAS provides a direct probe of ligand metal bonding. We have developed this methodology to investigate the electronic structures of model complexes and protein active-sites of a number of clusters and sites, in particular Fe-S, Cu-S clusters and dithiolene-containing Mo/W sites. In the previous proposal period, among several studies, we evaluated the generality of the difference between HiPIPs and ferredoxins and systematically studied the effect of H-bonding, solvent interaction and effect of changing dielectric field around these and other clusters using well-characterized model complexes and proteins, and combined experimental results with DFT calculation. We have also developed the bonding/geometric structure correlations in the Mo(tris)dithiolenes and the mechanism of oxo trasnsfer in the DMSO reductase family of enzymes and models. In this proposal we plan to extend this methodology, and combine it with complementary spectroscopies, to study several Fe-S systems, such as the interaction of SAM with the Fe4S4 cluster in pyruvate lyase activating enzyme; MutY - a DNA glycosylase from Escherichia coli; Fe2S2 protein binding to ?9 desaturase; and effects of Cys->Ser mutations on electron delocalization in iron sulfur clusters. We also intend to study a series of Mo mono- and bis-oxo bis(dithiolene) complexes that model the states of the sulfite oxidase family. The specific aim is to define the electronic structure of enzymes and model complexes and understand the correlations between structure and function of enzymatic reactions.