DISTANCE MEASUREMENTS IN METALLOPROTEINS

呼吸和光合作用中的能量转导涉及 电子转移反应与An生成的耦合 在双层膜上的电化学梯度。尽管 电子转移反应的顺序和动力学基本上是 在这些系统中已知的，对空间排列的了解要少得多 电子载体以及它们之间的距离。理想情况下， 电子载体可以被用作探针，以便解开它们的 电子的空间组织和长程电子转移距离 生物电子传输过程。这样做的长期目标是 项目是使用电子自旋松弛增强测量来 测定蛋白质中氧化还原活性部位之间的距离和探针 多核金属离子团簇的磁性。第一 目的是描述成对磁场的影响。 相互作用对电子自旋弛豫速率的影响 相互作用中心之间的距离和分子的磁性 每个中锋都是已知的。在这项研究中，来自于 RB Shaeroides将被用作模型系统。这种蛋白质可以是 在一种状态下制备的，该状态包含两个固定的顺磁性位置 距离为28埃。电子自旋弛豫速率的增强 细菌-叶绿素特殊对阳离子自由基的磁性 与非血红素Fe，或Fe-位中的Mn2+或Cu2+的相互作用将是 通过改变金属离子和温度来系统地研究 在非定向样本和定向样本中都有。这些数据将用于 对自旋弛豫增强理论进行了验证和推广。第二 目的是利用电子自旋-晶格弛豫速率的测量 增强以确定空间组织和磁性 细胞色素C氧化酶和光系统II，2中氧化还原位点的性质 结构信息是完整的膜蛋白复合体 不可用。将进行三种类型的申请，以便 获取这两个系统中的结构信息，并建立 此方法在确定其他区域的距离时的普遍适用性 系统。第一个应用是测量磁相互作用 在内源位置之间。第二是衡量两国之间的互动 内源性位点和外源性Dy3+-螯合物。三是 使用自旋晶格温度依赖关系的测量 光系统II中稳定酪氨酸自由基弛豫速率的探讨 研究了Mn团簇的磁性。这些实验将 为使用电子自旋-晶格弛豫测量提供了基础 确定电子转移距离和磁性的方法 其他氧化还原蛋白质络合物中的金属离子簇。

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 spatial arrangement of the electron carriers and the distances between them. Ideally, the electron carriers could be used as probes in order to unravel their spatial organization and the distances of long-range electron transfer in the biological electron-transport processes. The long-term goals of this project are to use electron spin relaxation enhancement measurements to determine distances between redox active sites in proteins and to probe the magnetic properties of multinuclear metal ion clusters. The first objective is to characterize the effects of pairwise magnetic interactions on the electron spin relaxation rates in samples in which the distance between interacting centers and the magnetic properties of each center are known. In this study, the reaction center protein from Rb sphaeroides will be used as a model system. This protein can be prepared in a state that contains two paramagnetic sites at a fixed distance of 28 Angstroms. The electron spin relaxation rate enhancement of the bacteriochlorophyll special pair cation radical due to a magnetic interaction with the nonheme Fe, or Mn2+ or CU2+ in the Fe -site, will be systematically investigated by varying the metal ions and the temperature in both non-oriented and oriented samples. These data will be used to test and extend the theories for spin relaxation enhancement. The second objective is to use measurements of electron spin-lattice relaxation rate enhancements to determine the spatial organization and magnetic properties of redox sites in cytochrome c oxidase and photosystem II, two integral membrane protein complexes for which structural information is not available. Three types of applications will be pursued in order to obtain structural information in these two systems and also to establish the general applicability of this method to determine distances in other systems. The first application is to measure magnetic interactions between endogenous sites. The second is to measure interactions between endogenous sites and an exogenous Dy3+-chelate complex. The third is to use measurements of the temperature dependence of the spin-lattice relaxation rate of the stable tyrosine radical in Photosystem ii to probe the magnetic properties of the Mn cluster. These experiments will 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.