Understanding Coupled Transfers of Electrons and Protons

描述（由申请人提供）：许多生物化学过程涉及电子和质子的耦合转移。这是一个关键步骤，例如，对于一系列酶（例如，细胞色素c氧化酶，光系统I和II，细胞色素P450）和捕获活性氧（例如，维生素E和超氧化物歧化酶）。拟议的研究的目标是发展这些过程的基本和预测性的理解。这种理解在一系列生物化学系统中将是有价值的，就像目前纯电子转移的知识非常有价值一样。拟议的工作包括各种化合物，反应和技术，以揭示化学的基本特征。 氢原子转移反应是该提案的主要焦点，建立在最近发现的一系列氢原子转移反应遵循马库斯交叉关系的基础上。Marcus方法能够预测反应速率，并基于驱动力和内在障碍为这些反应提供了新的基本直觉。内在屏障可以通过研究自交换率来测量，这将对许多化合物进行测定。电子，质子和氢原子转移的内在障碍之间的关系将被检查。扩展氢化物转移反应进行了讨论，包括可能的应用马库斯的方法。 新的化学体系将被开发，其中分子内质子转移耦合到分子间电子转移。这种质子耦合电子转移（PCET）过程是非常常见的，如在光系统II中的酪氨酸Z-组氨酸单元的氧化。它将确定质子转移之前，成功，或与电子转移在这样的系统中是一致的。采用一种或另一种机制的原因将被探讨，使用反应的内在障碍和热力学。涉及金属过氧化物络合物的化学反应也将被检查，两个反应的孤立的过氧化物和反应，可以形成O-O键。 拟议的工作采取了广泛的观点-研究铁，钴，锰，钌和锇系统和各种类型的反应-为了提供新的和有价值的见解，各种质子耦合电子转移发生在生物学。

DESCRIPTION (provided by applicant): Many biochemical processes involve the coupled transfer of electrons and protons. This is a key step, for instance, for a range of enzymes (e.g., cytochrome c oxidase, photosystems I and II, cytochromes P450) and in the trapping of reactive oxygen species (e.g., by vitamin E and superoxide dismutases). The goal of the proposed research is to develop a fundamental and predictive understanding of these processes. This understanding will be valuable in a range of biochemical systems, much as the current knowledge of pure electron transfer has been very valuable. The proposed work encompasses a variety of compounds, reactions, and techniques to uncover the essential features of the chemistry. Hydrogen atom transfer reactions are a primary focus of the proposal, building on the recent discovery that a range of H-atom transfer reactions follow the Marcus cross relation. The Marcus approach enables prediction of reaction rates and provides a new fundamental intuition for these reactions, based on driving force and intrinsic barriers. The intrinsic barriers can be measured through studies of self-exchange rates, which will be determined for a number of compounds. The relationship between the intrinsic barriers for electron, proton, and hydrogen atom transfer will be examined. Extensions to hydride transfer reactions are discussed, including possible application of the Marcus approach. New chemical systems will be developed in which an intramolecular proton transfer is coupled to intermolecular electron transfer. Such proton-coupled electron transfer (PCET) processes are very common, as in the oxidation of the tyrosine Z-histidine unit in photosystem II. It will be determined whether proton transfer precedes, succeeds, or is concerted with electron transfer in such systems. The reasons for adopting one mechanism or another will be probed, using the intrinsic barriers and thermodynamics of the reactions. Chemical reactions that involve metal peroxide complexes will also be examined, both reactions of isolated peroxides and reactions that could form O-O bonds. The proposed work takes a broad view - studying iron, cobalt, manganese, ruthenium and osmium systems and a variety of types of reactions - in order to provide new and valuable insights into the various kinds of proton-coupled electron transfer that occur in biology.