DISTANCE MEASUREMENTS IN METALLOPROTEINS

描述：（改编自申请人的摘要） 呼吸和光合作用涉及电子传递的耦合 反应产生跨双层的电化学梯度 膜的虽然电子转移反应的顺序和动力学 在这些系统中基本上是已知的，但对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 这个项目是开发和应用的方法，使用电子载体作为 探测器，以确定远程生物的距离和机制 电子转移与多核的结构和磁性 金属离子簇该提案的主要目的是使用电子 电子顺磁自旋弛豫增强测量与分析 共振（EPR）线型，以获得结构和磁性信息， 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 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 合成酶和其还原酶结构域。下一 目的在于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 一个结构化的模型系统进行系统的研究， 的距离，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弛豫的增强作用 叶绿素是一种特殊的阳离子对自由基，P700+被铁硫还原 簇A、B和X。这些信息对于精确的距离至关重要 在氧化还原蛋白质的电子转移伙伴之间的估计。此外，本发明还提供了一种方法， 内源性Dy ~（3+）螯合物作电子 自旋弛豫增强剂，以确定表面可及性 用蒙特卡罗方法扩展蛋白质中的顺磁中心 模拟蛋白质的排除体积和Dy 3+螯合物的分布 蛋白质周围的溶液中的复合物。总的来说，这些测量 将提供有关正在研究的系统的新信息， 提供了使用电子自旋晶格弛豫测量的基础， 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物中的簇。

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.