Understanding Coupled Transfers of Electrons and Protons

了解电子和质子的耦合转移

• 批准号: 6737573
• 负责人: JAMES M MAYER
• 金额: $ 27.87万
• 依托单位: UNIVERSITY OF WASHINGTON
• 依托单位国家: 美国
• 财政年份: 1995
• 资助国家: 美国
• 起止时间: 1995-02-01 至 2007-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6737573
• 关键词: X ray crystallography; active sites; chemical synthesis; chemical transfer reaction; covalent bond; electron spin resonance spectroscopy; electron transport; enzyme activity; enzyme mechanism; heavy metals; hydrocarbons; hydrogen ions; hydroxyl group; metal complex; metalloenzyme; nicotinamide adenine dinucleotide; nuclear magnetic resonance spectroscopy; oxidation

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.

描述（由申请人提供）：许多生化过程涉及电子和质子的耦合传递。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）和反应性氧物种（例如，通过维生素E和超氧化物歧化酶）的捕获，这是一个关键步骤。拟议的研究的目的是对这些过程进行基本和预测的理解。这种理解在一系列生物化学系统中将是有价值的，就像当前对纯电子转移的知识非常有价值。提出的工作涵盖了各种化合物，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重点，这是基于最近发现的，即一系列H原子转移反应遵循Marcus交叉关系。 MARCUS方法可以预测反应速率，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。可以通过研究自我交换率来测量固有障碍，该速率将确定多种化合物。将检查电子，质子和氢原子转移的内在屏障之间的关系。讨论了对氢化物转移反应的扩展，包括可能应用MARCUS方法。 将开发新的化学系统，其中分子内质子转移与分子间电子转移耦合。这种质子耦合的电子传输（PCET）过程非常普遍，就像光系统II中酪氨酸Z-依然氨酸单元的氧化中一样。将确定质子转移在此类系统中是否与电子传输进行了一致。采用一种或另一种机制的原因将使用反应的内在障碍和热力学进行探测。还将检查涉及金属过氧化金属复合物的化学反应，这两个反应的过氧化物和可能形成O-O键的反应的反应。 拟议的工作具有广阔的视野 - 研究铁，钴，锰，松和osmium系统以及各种反应 - 以便对生物学中发生的各种质子耦合电子转移提供新的和有价值的见解。