Coupled Transfers of Electrons and Protons

项目摘要/摘要 拟议的研究将寻求对以下方面的可访问性、概念性和量化的理解 质子耦合电子转移(PCET)过程，其中一个质子和一个电子以动力学方式耦合 但在反应物或产物中物理分离。尽管它们广泛存在于生物学领域，但这些 多位协同质子-电子转移反应(MS-CPET)还不是很清楚。例如, MS-CPET反应是生物能量过程的关键，是许多催化循环的中心 金属酶，并参与活性氧物种的化学。 拟议的研究将检查一系列小分子系统，以开发基本的 MS-CPET并对特定的生化过程进行建模。在理论的指导下，我们将找出关键 控制MS-CPET的参数。我们将研究电子和质子供体-受体的变化。 距离，中间介质的性质，以及整个驱动的电子和质子成分 MS-CPET的力。铁-卟啉络合物和Ru-多肽结构的研究进展 将提供涉及远程电子转移(ET)的MS-CPET的系统分析。酚类化合物的研究 含有酪氨酸的多肽将有助于阐明酶催化过程中酪氨酸自由基是如何形成的。 或在氧化应激下。采用新颖的蒽-苯酚-吡啶三元化合物，其中MS-CPET 成分都包含在同一分子中，我们将研究超快光诱导的MS-CPET 流程。该系统的显著特性首次提供了对 E−/H+双隧道事件，这是MS-CPET的特征。拟议的研究将阐明如何 分子水平上的结构变化会影响这种隧穿的概率。 MS-CPET几乎完全局限于OH和NH键的反应，其中质子 通过氢键转移。从具有定位的碱性或酸性基团的独特模型体系开始， 我们将展示涉及C-H键的MS-CPET反应可以非常容易。初步结果表明， 这些反应具有一些独特的性质。拟议的研究将发展第一个MS-CPET反应 这将裂解并形成C-H键，并将说明为什么这可能是一种常见的酶机制。 总之，这些研究的结果将建立新的概念性理解和可获得性 MS-CPET的定量模型。我们强调制定基本原则的灵感来自于 电子转移基础已成为生物化学的基础部分。建议的工作 在这里将建立一个类似的有价值的MS-CPET反应的理解，将适用于各种 生物过程。

PROJECT SUMMARY/ABSTRACT The proposed research will pursue an accessible, conceptual, and quantitative understanding of proton-coupled electron transfer (PCET) processes in which a proton and an electron are kinetically coupled but physically separated in the reactants or products. Despite their widespread presence across biology, these multiple-site concerted proton-electron transfer reactions (MS-CPET) are not well understood. For instance, MS-CPET reactions are key to bioenergetic processes, are central to the catalytic cycles of numerous metalloenzymes, and are involved in the chemistry of reactive oxygen species. The proposed studies will examine a range of small molecule systems to develop the fundamentals of MS-CPET and to model specific biochemical processes. With guidance from theory, we will identify the key parameters that control MS-CPET. We will examine changes in the electron and proton donor-acceptor distances, the nature of the intervening medium, and the electron and proton components of the overall driving force for MS-CPET. The proposed studies of iron-porphyrin complexes and of ruthenium-peptide constructs will provide systematic analyses of MS-CPET involving long-range electron transfer (ET). Studies of phenols and tyrosine-containing peptides will help elucidate how tyrosyl radicals are formed during enzymatic catalysis or under oxidative stress. Using novel anthracene-phenol-pyridine triads, in which all of the MS-CPET components are contained in the same molecule, we will examine ultrafast photo-induced MS-CPET processes. The remarkable properties of this system provide, for the first time, experimental access to the e−/H+ double tunneling event that is characteristic of MS-CPET. The proposed studies will elucidate how changes in structure at the molecular level affect the probability of this tunneling. MS-CPET has been almost completely limited to reactions of OH and NH bonds, in which the proton transfers across a hydrogen bond. Starting from unique model systems with positioned basic or acidic groups, we will show that MS-CPET reactions involving C–H bonds can be very facile. Preliminary results suggest that these reactions have some unique properties. The proposed studies will develop the first MS-CPET reactions that cleave and form C–H bonds, and will show why this is likely a common enzymatic mechanism. Together, the results from these studies will build new conceptual understanding and accessible quantitative models of MS-CPET. Our emphasis on developing basic principles is inspired by how the fundamentals of electron transfer have become a foundational part of biological chemistry. The work proposed herein will build a similarly valuable understanding of MS-CPET reactions that will be applicable to a variety of biological processes.