MODELS OF THE PHOTOSYNTHETIC WATER OXIDATION CENTER

形态描述：在植物的光合机构中， 植物和蓝藻是质子和电子的来源 用于CO2固定/碳水化合物合成以促进健康生长。 在 此外，放出的氧气（O2）副产物代表了 大气中的这种气体，因此这种反应也影响了 维持这个星球上所有生命的健康 水 氧化络合物（WOC）是一种含四个锰的金属单元 由氧离子（O2-）桥接并保持在宿主多肽上的原子 主要通过氨基酸侧链的羧酸酯官能团。 的 阐明了WOC的性质和作用机制， 当前最重要、最艰巨的挑战之一， 金属生物化学。 为促进实现这一目标， 所提出的工作涉及WOC Mn/O/RCO 2簇合物的合成 在实验室里，而不是从植物中分离出来。 这种合成 附加方法的优点是可以获得更大的量 比通常可从植物来源获得的多，以及外周连接 可以是小的有机羧酸盐而不是多肽。 因此 可以使用多种光谱和物理化学技术 在较短的时间范围内提供更大量的数据， 达到比原生站点可能的更高的精确度。 以前的工作提供了合成进入所需类型的 四核Mn/O/RCO 2配合物，和拟议的工作将扩大 研究结构和其他性能，然后进行比较， 与天然WOC的多氧化态形成对比;这是 除其他外，旨在便利解释一些不寻常的 WOC的属性。 此外，高氧化的合成类似物 对应于O2释放前WOC状态的状态 将通过电化学产生并研究它们的能力 为了释放O2，后一反应的成功实现将提供 一个系统，将服从随后详细的动力学和 机制研究，提供关于 两个H2O分子与O2的氧化偶联以及 中间体，例如，金属结合的过氧化物基团。

DESCRIPTION: Water oxidation within the photosynthetic apparatus of plants and cyanobacteria represents a source of protons and electrons for CO2 fixation/carbohydrate synthesis for healthy growth. In addition, the evolved oxygen (O2) by-product represents the source of this gas in the atmosphere, and thus this reaction also impacts the health and maintenance of all respiring life on this planet. The water oxidation complex (WOC) is a metallo-unit containing four manganese atoms bridged by oxide (O2-) ions and held to the host polypeptides primarily by carboxylate functionalities of amino acid side-chains. The elucidation of the nature and mechanism of action of the WOC represents one of the most important and toughest current challenges within Metallobiochemistry. To facilitate the attainment of this objective, the proposed work involves the synthesis of the WOC Mn/O/RCO2 cluster in the laboratory rather than its isolation from plants. This Synthetic Analogue Approach has the advantage that larger amounts can be obtained than are normally available from plant sources, and peripheral ligation can be small organic carboxylates rather than polypeptides. Thus, a wide variety of spectroscopic and physicochemical techniques can be employed providing a greater amount of data in a shorter time frame and to a higher degree of precision than is possible for the native site. Previous work has provided synthetic entry into the desired type of tetranuclear Mn/O/RCO2 complexes, and the proposed work will extend the study of structural and other properties, followed by comparisons and contrasts with the multiple oxidation states of the native WOC; this is designed, inter alia, to facilitate interpretation of several unusual properties of the WOC. Further, synthetic analogues in high oxidation states corresponding to those of the WOC states preceding O2 evolution will be electrochemically generated and investigated for their ability to evolve O2, successful attainment of the latter reaction will provide a system that would be amenable to subsequent detailed kinetic and mechanistic study, providing fundamental information on the mechanism of oxidative coupling of two H2O molecules to O2 and the identify of intermediates, e.g., metal-bound peroxide groups.