ELECTRON TRANSFER PROCESSES IN IRON AND COPPER PROTEINS

电子转移(ET)反应在许多生物中起着关键作用 流程。在这些系统中，供体和受体部位可以是 以10-25埃为单位的距离分隔。我们的目标是 探讨控制远程ET率的因素：SITE- 到位点的距离、驱动力、介入性蛋白质的性质 中等和氧化还原中心，以及重组能量。我们 打算研究和比较分子内远程ET 结构良好的Ru(II/III)衍生物中的反应- 铁和铜的特征蛋白：牛细胞色素b5， 脱氮产碱菌天青素和高电势铁硫 红色变色菌、玫瑰花冠藻和花生型变色菌蛋白质 [医]纤细染色属。我们还打算研究老鼠的突变 细胞色素b5，其修饰设计用于解决介质 和系统的距离效应。 今后三年，我们建议：(1)高度准备 上述野生型和突变型蛋白的纯化样品 在选定的表面组氨酸残基上用Ru标记 (ii/iii)试剂；(2)通过以下方式表征这些修饰的蛋白质 光谱和电化学测量；(3) 用闪光光解实验测定ET的速率 在蛋白质氧化还原中心(铁-血红素或其他金属)之间 卟啉、蓝铜或铁-硫团簇)和表面- 结合的Ru；以及(4)分析电子(距离， 中等)和精力充沛(动力、重组能量、 温度)中的长程ET率分量 典型的血红素、蓝色库珀和铁硫蛋白。 拟议的实验将使我们能够开发出更好的 对所有生物必不可少的一个基本过程的理解 有机体。

Electron-transfer (ET) reactions play a key role in many biological processes. In these systems the donor and acceptor sites can be separated by distances of 10-25 angstrom unit. Our aim is to probe the factors that control the rates of long-range ET: site- to-site distance, driving force, nature of the intervening protein medium and of the redox centers, and reorganization energy. We intend to study and to compare intramolecular long-range ET reactions in ruthenium (II/III) derivatives of structurally well- characterized iron and copper proteins: bovine cytochrome b5, Alcaligenes denitrificans azurin, and high-potential iron-sulfur proteins from Chromatium vinosum, Thiocapsa roseopersicina, and Chromatium gracile. We also intend to study mutants of rat cytochrome b5 with modifications designed to address medium and distance effects systematically. During the next three years, we propose: (1) to prepare highly purified samples of the above wild-type and mutant proteins labeled at selected surface histidine residues with ruthenium (II/III) reagents; (2) to characterize these modified proteins by spectroscopic and electrochemical measurements; (3) to determine by flash photolysis experiments the rates of ET between the protein redox center (iron-heme or other metal phorphyrin, blue copper, or iron-sulfur cluster) and the surface- bound ruthenium; and (4) to analyze the electronic (distance, medium) and energetic (driving force, reorganization energy, temperature) components of the long-range ET rates in these prototypal heme, blue cooper, and iron sulfur proteins. The proposed experiments will allow us to develop a better understanding of a fundamental process essential to all living organisms.