DISTANCE MEASUREMENTS IN METALLOPROTEINS

描述：(改编自申请者摘要)能量转导 呼吸作用和光合作用涉及电子传递的耦合。 在两层膜上产生电化学梯度的反应 薄膜。尽管电子转移反应的顺序和动力学 在这些系统中大体上是已知的，关于距离的了解要少得多 以及电子载体之间的电子耦合。的长期目标 该项目是开发和应用方法，以使用电子载体作为 用于确定远程生物的距离和机制的探头 电子转移与多核化合物的结构和磁性 金属离子团簇。这项提议的主要目标是使用电子 电子顺磁的自旋弛豫增强测量与分析 共振(EPR)线条形状，以获取其结构和磁性信息 光系统II和一氧化氮合酶。具体目标是确定 氧化还原中心的空间组织，活性中心的结构 对于水的氧化和锰团簇的磁性 光系统II，并表征一氧化氮的构象变化 合酶及其还原酶域在被钙调蛋白激活时。下一个 目标是改进使用自旋弛豫的方法 增强测量以确定距离。光系统I将被用作 进行系统研究的具有结构特征的模型系统 距离、取向、g各向异性和自旋分布的影响 金属离子团簇对电子自旋-晶格驰豫的增强作用 叶绿素一种特殊的阳离子对自由基P700+，由铁硫还原而成 群集A、B和X。此信息对于精确距离至关重要 氧化还原蛋白质中电子转移伙伴之间的估计。此外, 利用内源Dy3+-络合物作为电子的方法 用于确定表面可及性的自旋弛豫增强剂 用蒙特卡罗方法扩展蛋白质中的顺磁中心 排除蛋白体积和Dy3+-络合物分布的模拟 蛋白质周围的溶液中的络合物。总体而言，这些衡量标准 将提供有关正在研究的系统的新信息，并将 为使用电子自旋-晶格弛豫测量提供基础 测定金属离子的电子转移距离和磁性 其他氧化还原蛋白复合体中的簇状结构。

DESCRIPTION: (Adapted from the Applicant's Abstract) Energy transduction in respiration and photosynthesis involves the coupling of electron-transfer reactions to the generation of an electrochemical gradient across a bilayer membrane. Although the sequence and kinetics of the electron-transfer reactions are by and large known in these systems, much less is known about the distances and electronic couplings between the electron carriers. The long term goals of this project are to develop and apply methods to use the electron carriers as probes to determine the distances and mechanisms of long-range biological electron transfer and the structure and magnetic properties of multinuclear metal ion clusters. The primary objective of this proposal is to use electron spin relaxation enhancement measurements and analysis of electron paramagnetic resonance (EPR) line shapes to obtain structural and magnetic information on photosystem II and nitric oxide synthase. The specific aims are to determine the spatial organization of the redox centers, the structure of the active site for water oxidation and the magnetic properties of the manganese cluster in photosystem II, and to characterize the conformational changes of nitric oxide synthase and its reductase domain upon activation by calmodulin. The next objectives are aimed at improving the methods for using spin relaxation enhancement measurements to determine distances. Photosystem I will be used as a structurally characterized model system to carry out a systematic study of the effects of distance, orientation, g-anisotropy, and spin distribution in a metal ion cluster on electron spin-lattice relaxation enhancement of the chlorophyll a special pair cation radical, P700+, by the reduced iron-sulfur clusters A, B, and X. This information is essential for accurate distance estimates between electron-transfer partners in redox proteins. In addition, the method of using endogenous Dy3+-chelate complexes as electron spin-relaxation enhancement agents to determine the surface accessibility of paramagnetic centers in proteins will be extended by using a Monte Carlo method to model the excluded protein volume and the distribution of Dy3+-chelate complexes in the solution surrounding the protein. Overall, these measurements will provide new information about the systems under study and will also provide a basis for using electron spin-lattice relaxation measurements to determine distances of electron transfer and magnetic properties of metal ion clusters in other redox protein complexes.