HALIDE XAS STUDIES OF PHOTOSYNTHETIC WATER OXIDATION COMPLEX

光合作用的水氧化是由4个锰原子簇催化的 原子。氯化物和钙是氧气的重要辅助因子 进化活动。据推测，卤化物是一种配体 MN，但目前的证据并不确凿。CL K-EDGE研究 作者：Hedman et al(Hedman，B.，Hodgson，K.O.&所罗门，E.I.(1990)J. 上午好。化学。SoC。112,1643-1645)表明，有一种独特的 氯的K-边谱中的前缘特征 过渡金属。该要素已分配给CL 1S至金属3D 跃迁，由于与空的d轨道混合而变得允许。 这种前缘特征仅在氯离子与金属连接时才出现 有空的d轨道。我们建议收集氯的K-边光谱 光系统II样本仅包含最少量的 CL-活性所必需的(1CL/4MN)，以确定是否连接了氯 转到MN。

Photosynthetic water oxidation is catalyzed by a cluster of 4 Mn atoms. Chloride and calcium are essential cofactors for oxygen evolution activity. It has been postulated that halide is a ligand to Mn, but the evidence at present is not conclusive. Cl K-edge studies by Hedman et al (Hedman, B., Hodgson, K.O. & Solomon, E.I. (1990) J. Am. Chem. Soc. 112, 1643-1645) have shown that there is a distinctive pre-edge feature in the K-edge spectrum of Cl when it is a ligand to transition metals. The feature was assigned to a Cl 1s to metal 3d transition, which becomes allowed due to mixing with empty d-orbitals. Such a pre-edge feature is present only when Cl- is ligated to a metal with empty d-orbitals. We propose to collect Cl K-edge spectra of photosystem II samples containing only the minimal amount of Cl-required (1Cl/4Mn) for activity to determine whether Cl is ligated to Mn.