PES/DFT STUDIES ON ELECTRONIC STRUCTURE CONTRIBUTIONS TO ELECTRON TRANSFER

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来源获得主要资金，因此可以在其他CRISP条目中表示。所列机构为中心，不一定是研究者所在机构。我们的研究重点是应用可变能量光电子能谱（PES）结合X射线吸收边谱（XAS）来确定电子结构对生物系统中电子转移（ET）的贡献。PES提供了一种直接的方法来研究无机氧化还原过程和电子弛豫对氧化还原性质的贡献（E，HAB，l）。核心和价PES数据中存在的震荡卫星结构可以与价键构型相互作用（VBCI）模型结合使用，以实验方式量化电子弛豫（即氧化后金属络合物电子结构的变化）及其对ET还原电位和动力学的贡献。可变能量PES实验提供了一种机制，以最大限度地提高金属，同时通过横截面效应（延迟最大值和库珀最小值）和共振增强最小化配体的贡献的价带区域。我们对简单模型体系[FeX_4]~（2-）/~（1-）（X=Cl ~-，-SR）的同步加速器研究提供了定义电子结构及其在氧化还原过程中变化的实验结果。补充密度泛函理论（DFT）计算，这些研究提供了深入了解电子弛豫，并允许扩展到金属蛋白质网站。使用[FeX 4]2-/1研究中开发的方法，我们现在正在研究模型血红素复合物。血红素模型结合DFT计算的数据也应该允许扩展和定义ET在细胞色素中的超交换途径。我们还将这些PES/DFT研究扩展到[Fe 4S 4（SR）4]系统建模的4Fe铁氧化还原蛋白和HiPIPS（高电位铁蛋白），这将提供深入了解电子弛豫及其对铁氧化还原蛋白和HiPIPS中ET的动力学和途径的贡献。

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. The major emphasis of our research is to apply variable energy photoelectron spectroscopy (PES) combined with X-ray absorption edge spectroscopy (XAS) to define electronic structure contributions to electron transfer (ET) in biological systems. PES provides a direct method to study inorganic redox processes and the contribution of electronic relaxation to redox properties (E¿¿, HAB, l). The shake-up satellite structure present in core and valence PES data can be used in combination with a valence bond configuration interaction (VBCI) model to experimentally quantify electronic relaxation (i.e. the change in electronic structure of metal complexes upon oxidation) and its contributions to reduction potentials and kinetics of ET. Variable-energy PES experiments provide a mechanism to maximize the metal while minimizing the ligand contributions to the valence band region through cross section effects (delayed maximum and Cooper minimum) and resonance enhancement. Our synchrotron-based studies on simple model systems [FeX4]2-/1 (X=Cl-, -SR) have afforded experimental results that define electronic structure and its changes upon redox. Complemented by density functional theory (DFT) calculations, these studies provide insight into electronic relaxation and allow extension to the metalloprotein sites. Using the methodology developed in the studies on [FeX4]2-/1, we are now examining model heme complexes. The data on the heme models combined with DFT calculations should also allow extention to and define the superexchange pathways for ET in the cytochromes. We will also extend these PES/DFT studies to [Fe4S4(SR)4] systems modeling the 4Fe ferredoxins and HiPIPs (high potential iron proteins), which will provide insight into electronic relaxation and its contributions to the kinetics and pathways for ET in the ferredoxins and HiPIPS.