MODELS OF THE PHOTOSYNTHETIC WATER OXIDATION CENTER

光合水氧化中心模型

• 批准号: 2900664
• 负责人: GEORGE CHRISTOU
• 金额: $ 18.69万
• 依托单位: TRUSTEES OF INDIANA UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1988
• 资助国家: 美国
• 起止时间: 1988-02-01 至 2001-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2900664
• 关键词: X ray crystallography; algae; ammonia; carbon dioxide; carbon dioxide fixation; chloroplasts; enzyme complex; manganese; metal complex; model design /development; oxidation; oxygen; peroxides; photosynthetic reaction centers; physical model; protein biosynthesis; protein structure function; spectrometry; synthetic protein; water

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.

描述：光合作用机构内的水氧化作用 植物和蓝藻是质子和电子的来源 用于二氧化碳固定/碳水化合物合成，以促进健康生长。在……里面 此外，放出的氧气(O2)副产物代表了 大气中的这种气体，因此这个反应也会影响 地球上所有呼吸的生命的健康和维持。这水 氧化络合物(WOC)是一个含有四个锰的金属单元 氧(O2-)离子桥联的原子与宿主多肽结合 主要是由氨基酸侧链的羧化官能团决定的。这个 阐明WOC代表的作用性质和机制 目前最重要和最严峻的挑战之一是 代谢生物化学。为促进实现这一目标， 建议的工作包括合成WOC Mn/O/RCO2团簇 在实验室里，而不是与植物隔离。这种合成物 类比法的优点是可以获得更大的量 比通常从植物来源获得的更多，以及外周结扎 可以是小分子有机羧酸盐，而不是多肽。因此，一个 各种各样的光谱和物理化学技术可以 采用在较短的时间范围内提供更大量的数据以及 达到比本机站点更高的精确度。 以前的工作已经提供了进入所需类型的合成入口 四核Mn/O/RCO2络合物，拟议的工作将延长 对结构和其他性质的研究，随后是比较和 与天然WOC的多种氧化状态形成对比；这是 除其他外，旨在便利解释几个不寻常的 WOC的属性。此外，高氧化中的合成类似物 与O2演化之前的WOC状态相对应的状态 将被电化学产生，并被研究其能力 为了放出O2，成功实现后一反应将提供 一个系统将服从于随后详细的动力学和 机械学研究，提供了关于 两个H2O分子对O2的氧化偶联及其鉴定 中间体，例如金属结合的过氧化氢基团。