ELECTRON TRANSFER PROCESSES IN IRON AND COPPER PROTEINS

电子转移（ET）反应，最简单的化学反应 过程，渗透到生物学中。 光合作用，呼吸作用，固氮作用， 药物代谢、DNA合成和免疫反应代表一小部分 ET反应在许多生物过程中起着关键作用 角色 任何试图理解结构和 氧化还原酶的功能依赖于对长距离ET的理解， proteins. 先前的理论和实验工作表明，不同的蛋白质 二级结构类型介导长距离ET， 效率。 我们将对距离进行系统的测量， ET速率对β-折叠（天青蛋白，amicyanin， 可溶性Cu（a）和α-螺旋（细胞色素B（562））蛋白， 定义远程ET效率和氢键的作用， 这两个结构。 理论模型表明，远程ET的效率取决于 氧化还原位点的电子态的相对能量和 蛋白质基质（多肽）。 从来没有一个明确的实验 这种所谓的隧道能量依赖的演示，但 预测的效果可能相当显著。 隧穿能量在 远距离ET将在距离依赖性研究中进行评估， ET率在几种蛋白质作为受体还原电位的函数。 金属络合物在电子转移中经常充当氧化还原位点 proteins. 长程ET取决于耦合这些氧化还原的效率 插入多肽的位点。 由于不同的金属配体 由于相互作用，这种耦合可以是高度各向异性的。 成效为何 不同的配体偶联将在ET研究中进行检查， 铜蛋白天青蛋白的活性位点突变体。 许多生物氧化还原反应都伴随着 蛋白质构象 金属蛋白中的一个常见例子是增益或 在金属氧化态改变时活性部位的配体损失。 氧化还原偶联配位变化的动力学后果将是 在铜蛋白amicyanin的ET研究中进行了检查。

DESCRIPTION: Electron-transfer (ET) reactions, the simplest chemical processes, pervade biology. Photosynthesis, respiration, nitrogen fixation, drug metabolism, DNA synthesis, and immune response represent a small subset of the scores of biological processes in which ET reactions play pivotal roles. Any effort to understand the relationship between structure and function in redox enzymes rests on an understanding of long-range ET in proteins. Prior theoretical and experimental work indicates that different protein secondary-structure types mediate long-range ET with markedly different efficiencies. We will perform systematic measurements of the distance and deuterium isotope dependencies of ET rates on beta-sheet (azurin, amicyanin, soluble Cu(a) and alpha-helical (cytochrome b(562) proteins in order to define the long range ET efficiencies and the role of hydrogen bonds in these two structures. Theoretical models indicate that the efficiency of long-range ET depends on the relative energies of the electronic states of the redox sites and the protein matrix (polypeptide). There has never been a clear experimental demonstration of this so-called tunneling-energy dependence, yet the predicted effects can be quite significant. The role of tunneling energy in long-range ET will be evaluated in studies of the distance dependencies of ET rates in several proteins as functions of acceptor reduction potential. Metal complexes frequently serve as redox sites in electron-transfer proteins. Long-range ET depends on the efficiency of coupling these redox sites to the intervening polypeptide. Owing to varied metal-ligand interactions, this coupling can be highly anisotropic. The effects of these disparate ligand couplings will be examined in ET studies of several active-site mutants of the copper protein azurin. Many biological redox reactions are accompanied by significant changes in protein conformation. A common example in metalloproteins is the gain or loss of a ligand at the active site upon change in metal oxidation state. The kinetic consequences of a redox-coupled coordination change will be examined in ET studies of the copper protein amicyanin.