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首页> 美国卫生研究院文献>Proceedings of the National Academy of Sciences of the United States of America >Synthetic model of the asymmetric Mn3CaO4 cubane core of the oxygen-evolving complex of photosystem II
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Synthetic model of the asymmetric Mn3CaO4 cubane core of the oxygen-evolving complex of photosystem II

机译：光系统II释氧复合物的不对称Mn3CaO4古巴核心的合成模型

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The laboratory synthesis of the oxygen-evolving complex (OEC) of photosystem II has been the objective of synthetic chemists since the early 1970s. However, the absence of structural information on the OEC has hampered these efforts. Crystallographic reports on photosystem II that have been appearing at ever-improving resolution over the past ten years have finally provided invaluable structural information on the OEC and show that it comprises a [Mn3CaO4] distorted cubane, to which is attached a fourth, external Mn atom, and the whole unit attached to polypeptides primarily by aspartate and glutamate carboxylate groups. Such a heterometallic Mn/Ca cubane with an additional metal attached to it has been unknown in the literature. This paper reports the laboratory synthesis of such an asymmetric cubane-containing compound with a bound external metal atom, [(>1)] . All peripheral ligands are carboxylate or carboxylic acid groups. Variable-temperature magnetic susceptibility data have established >1 to possess an S = 9/2 ground state. EPR spectroscopy confirms this, and the Davies electron nuclear double resonance data reveal similar hyperfine couplings to those of other MnIV species, including the OEC S2 state. Comparison of the X-ray absorption data with those for the OEC reveal >1 to possess structural parameters that make it a close structural model of the asymmetric-cubane OEC unit. This geometric and electronic structural correspondence opens up a new front in the multidisciplinary study of the properties and function of this important biological unit.
机译：自1970年代初以来，光化学系统II的放氧复合物（OEC）的实验室合成一直是合成化学家的目标。但是，由于缺乏关于OEC的结构性信息，这些工作受到了阻碍。过去十年来，以不断提高的分辨率出现的有关光系统II的晶体学报告终于在OEC上提供了宝贵的结构信息，并显示它包含[Mn3CaO4]扭曲的古巴铝，并附有第四个外部Mn原子，并且整个单元主要通过天冬氨酸和谷氨酸羧化物基团与多肽连接。在文献中还不知道这种杂金属Mn / Ca古巴烷与附加的金属结合。本文报道了这种具有不对称外部金属原子[（> 1 ）]的不对称含古巴化合物的实验室合成方法。所有外围配体都是羧酸根或羧酸基团。可变温度磁化率数据已建立> 1 以具有S = 9/2基态。 EPR光谱证实了这一点，戴维斯电子核双共振数据显示出与其他Mn IV 物种（包括OEC S2状态）相似的超精细偶联。将X射线吸收数据与OEC的X射线吸收数据进行比较，发现> 1 具有结构参数，使其成为非对称古巴OEC单元的紧密结构模型。这种几何和电子结构的对应关系为该重要生物学单元的性质和功能的多学科研究开辟了新的领域。

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