HALIDE XAS STUDIES OF PHOTOSYNTHETIC WATER OXIDATION COMPLEX

4 Mn簇合物催化光合水氧化 原子的 氯和钙是氧的重要辅助因子 进化活动。 据推测，卤化物是 嗯，但是目前的证据还不是决定性的。 Cl K边研究 由Hedman等人（Hedman，B.，Hodgson，K.O. &所罗门，E.I.（1990）J. Am. 112，1643-1645）已经表明，存在一种独特的 当Cl是配体时，Cl的K边光谱中的前边特征 过渡金属 该特征被分配给Cl 1 s到金属3d 跃迁，这是由于与空d轨道混合而允许的。 只有当Cl-连接到金属上时，才会出现这种前边缘特征 d轨道是空的 我们建议收集以下物质的Cl K边缘光谱 光系统II样品仅含有最少量的 确定Cl是否连接的活性所需Cl（1Cl/4 Mn） 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.