ELECTRONIC STRUCTURE OF IRON ENZYME INTERMEDIATES FROM HIGH-RESOLUTION RIXS

该子项目是利用 由NIH/NCRR资助的中心赠款提供的资源。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。列出的机构是 中心，不一定是研究者的机构。 拟议的研究的目标是开发1 s2 p共振非弹性X射线散射（RIXS）作为一种通用的和定量的工具，用于研究酶的中间体。我们之前已经在SSRL使用金属L边光谱来扩展金属配体共价的概念，通过显示L边带形状可以用于量化配体和不同对称性的金属d轨道之间的相互作用，即，微分轨道共价（DOC）。DOC方法允许实验确定化学中的基本概念。然而，金属L边光谱是在超高真空中用软X射线进行的，通常不能用于酶中间体。1 s2 p RIXS涉及从1 s 3d（h ~ 7.1 keV）激发并监测随后的2 p 1 s光子发射（h ~ 2 ~ 6.4 keV）。这个共振过程的最终状态是2 p53 dn +1，与L边实验的最终状态相同。1 s2 p RIXS使用硬X射线，不需要超高真空，因此可以在原位条件下获得类似L边的光谱。我们的新贡献是在能量转移（h -h 2）方向使用DOC分析的RIXS光谱的定量分析。长寿命的2 p孔的结果在一个尖锐的和功能丰富的光谱，可以准确地拟合使用参数化的多重态模型，包括配置相互作用。电子结构，包括DOC，随后从理论模型中提取。该方法将被用来研究高价酶的中间体，激活惰性C？H键;血红素化合物I和II、SyrB 2中的非血红素铁酰基-氧代中间体和双核铁酶甲烷单加氧酶中的中间体Q。RIXS提供了一个新的工具来调查的要求，C？H键的活化，但也可以解释血红素和非血红素酶之间的反应性差异。

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 goal of the proposed research is to develop 1s2p resonant inelastic x-ray scattering (RIXS) as a general and quantitative tool for studying enzyme intermediates. We have previously used metal L-edge spectroscopy at SSRL to extend the concept of metal-ligand covalency by showing that the L-edge band shape can be used to quantify interactions between ligands and metal d-orbitals of different symmetry, i.e., differential orbital covalency (DOC). The DOC method allows for experimental determination of basic concepts in chemistry. However, metal L-edge spectroscopy is performed with soft x-rays in ultra-high vacuum and cannot in general be used for enzyme intermediates. 1s2p RIXS involves excitation from 1s 3d (h ~ 7.1 keV) and monitoring of the subsequent 2p 1s photon emission (h2 ~ 6.4 keV). The final state in this resonance process is 2p53dn+1, the same final state as for the L-edge experiment. 1s2p RIXS uses hard x-rays and does not require ultra-high vacuum, and can therefore be used to obtain L-edge-like spectra under in situ conditions. Our new contribution is a quantitative analysis of RIXS spectra in the energy transfer (h - h2) direction using the DOC analysis. The long life time of the 2p hole results in a sharp and feature-rich spectrum that can be accurately fitted using a parameterized multiplet model that includes configuration interaction. The electronic structure, including the DOC, is subsequently extracted from the theoretical model. The method will be used to study high-valent enzyme intermediates that activate inert C?H bonds; heme compounds I and II, the non-heme ferrryl-oxo intermediate in SyrB2 and intermediate Q in the binuclear iron enzyme methane monooxygenase. RIXS provides a new tool to investigate the requirements for C?H bond activation, but also to explain differences in reactivity between heme and non-heme enzymes.