HALIDE XAS STUDIES OF PHOTOSYNTHETIC WATER OXIDATION COMPLEX

光合水氧化由 4 Mn 簇催化 原子。 氯和钙是氧气的重要辅助因子 进化活动。 据推测，卤化物是配体 嗯，但目前的证据还不是决定性的。 Cl K 边缘研究 作者：Hedman 等人（Hedman, B.、Hodgson, K.O. 和 Solomon, E.I. (1990) J. 上午。化学。 苏克。 112, 1643-1645）已经表明，有一个独特的 当 Cl 为配体时，其 K 边光谱中的前边特征 过渡金属。 该特征被分配给 Cl 1s 到金属 3d 跃迁，由于与空 d 轨道混合而被允许。 仅当 Cl- 连接至金属时，才会出现这种预边缘特征 具有空的 d 轨道。 我们建议收集 Cl K 边缘光谱 光系统 II 样品仅含有最少量的 确定 Cl 是否连接的活性需要 Cl (1Cl/4Mn) 至锰。

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.