MODELS OF THE PHOTOSYNTHETIC WATER OXIDATION ENZYME

迄今公认的金属最重要的生物学作用 锰是一种催化水的锰酶。 在光合作用装置内氧化成氧气(O2) 高等植物和藻类。阐明其结构和作用机制 这个系统的作用范围代表了一个强烈的洋流区域 在生化社区内的活动。以允许详细说明 关于将在原子水平上获得的锰位的信息， 小分子的可用性是非常可取的。 锰络合物作为原生单元的模型。这样的模型 将对EPR和EXAFS的研究提供宝贵的帮助 酶，并允许获得机械细节，例如 底物结合的可能模式和后续的机制 底物氧化。目前还没有令人满意的型号， 然而，它们的合成和研究代表着主要的 这一研究计划的重点。初步结果描述了 第一批与酶有显著相关性的锰络合物 现在已经合成了。这些物种已经表现出几个 符合已知性质和结构的特征 酶上可用的参数。EXAFS、EPR和固态 建议进行磁学研究以进一步定义 可利用的合成物种与 自然锰位。该计划的综合扩展将寻求 修饰其结构、连接类型和氧化水平 可获得的材料允许更广泛和更详细 比较。这种材料的可获得性还允许 研究底物结合的可能性，重现 实验室条件下的水氧化反应，以及 阐明和中间体的机械细节在 催化循环。因此，拟议的计划代表了一种 持续进行中的基本组成部分和迄今无法获得的组成部分 对这一重要生物的多学科调查 系统。

The most important biological role yet recognized for the metal manganese (Mn) is the Mn enzyme which catalyzes water oxidation to dioxygen (O2) within the photosynthetic apparatus of higher plants and algae. Elucidating the structure and mechanism of action of this system represents an area of intense current activity within the biochemical community. To allow detailed information on the Mn site to be obtained at an atomic level, the availability would be highly desirable of small molecular weight Mn complexes to act as models of the native unit. Such models would be invaluable to assist in epr and EXAFS studies of the enzyme, and to allow mechanistic detail to be obtained, such as possible modes of substrate binding and mechanism of subsequent substrate oxidation. No satisfactory models have been available, however, and their synthesis and study represents the primary focus of this research program. Preliminary results described how the first Mn complexes of significant relevance to the enzyme have now been synthesized. These species already display several features in accord with known properties and structural parameters available on the enzyme. EXAFS, epr and solid-state magnetic studies are proposed to further define the correspondence between available synthetic species and the native Mn site. Synthetic extensions to the program will seek to modify the structures, ligation type and oxidation levels of attainable materials to allow broader and more detailed comparisons. Availability of such materials also allows the possibility of investigating substrate binding, reproducing the water oxidation reaction under laboratory conditions, and elucidating the mechanistic detail of and intermediates during the catalytic cycle. The proposed program thus represents an essential and hitherto unavailable component of the ongoing multi-disciplinary investigation of this important biological system.