ELECTRON EXCHANGE EFFECTS ON ELECTRON TRANSFER DYNAMICS

电子交换对电子传递动力学的影响

• 批准号: 2908203
• 负责人: JAMES K MCCUSKER
• 金额: $ 9.02万
• 依托单位: UNIVERSITY OF CALIFORNIA BERKELEY
• 依托单位国家: 美国
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-08-01 至 2001-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2908203
• 关键词: charge transfer complex; chemical transfer reaction; dimer; electron transport; intermolecular interaction; ionic bond; iron compounds; metalloproteins; molecular dynamics

DESCRIPTION: (Verbatim from the Applicant's Abstract) There exist in nature a remarkably large number of metalloproteins and metalloenzymes whose active sites consist of more than one metal center. In some cases these metals exist independently, while in others the several metal centers comprise a polynuclear cluster. In systems such as these (e.g., non-heme iron-oxo proteins and iron-sulfur proteins), the electronic structures of the polynuclear clusters are largely determined by electron exchange interactions that exist amongst the various metal centers. This research project is aimed at elucidating whether or not the electron exchange present in such polynuclear metal clusters can itself play a functional role in biological processes: the specific target of interest is electron transfer. A model is described wherein variations in electron exchange coupling can be linked to changes in both the driving force and reorganization energies associated with electron transfer into and out of an exchange-coupled metal cluster. The objective of this research is to experimentally establish whether or not such a model is viable in systems in which metal clusters are involved in the electron transfer pathway. Due to the complex nature of metalloproteins, identification of electron exchange influences on biological function requires some a priori knowledge of the possible effects one might observe. This type of information is completely lacking in the literature. Studies described herein therefore focus on synthetically tailored molecules in which all aspects of electronic and molecular structure are under experimental control. The research represents a blend of both synthetic inorganic and physical-inorganic chemistries, in which synthesis is coupled with detailed spectroscopic studies ranging from static absorption measurements to femtosecond time-resolved probes of electron transfer. Both inter- and intra-molecular electron transfer is being studied in model complexes containing both the oxo-bridged diiron(III) core as well as two-center iron-sulfur clusters. Molecules are prepared in which variations in exchange coupling are systematically introduced (probed by variable-temperature magnetic measurements). Electron transfer kinetics are then monitored using a variety of static and time-resolved spectroscopies (e.g., absorption, emission, and vibrational). The intermolecular studies take the form of classic Stern-Volmer-type quenching studies, whereas the intramolecular dynamics are probed through synthetically-tailored systems employing covalently linked electron donors and acceptors. It is believed that establishing whether or not electron exchange can play a functional role in electron transfer processes will represent a significant conceptual step forward for understanding electron transfer reactions in general, as well as lending specific insights into the role of polynuclear metal clusters in transition metal-containing proteins.

描述：（逐字来自申请人的摘要）在自然界中存在一种 大量的金属蛋白和金属酶， 站点由多于一个金属中心组成。在某些情况下，这些金属 在其它实施方案中，所述几个金属中心独立地包含多核金属中心，而在其它实施方案中，所述几个金属中心独立地包含多核金属中心。 集群在诸如这些的系统中（例如，非血红素铁氧蛋白， 铁硫蛋白），多核团簇的电子结构 在很大程度上取决于存在于 各种金属中心。该研究项目旨在阐明 在这种多核金属簇中存在的电子交换本身不能 在生物过程中发挥功能作用：感兴趣的特定目标 是电子转移。描述了一种模型，其中电子的变化 交换耦合可以与驱动力和 重组能量与电子转移进入和离开一个 交换耦合金属簇。本研究的目的是 实验性地确定这样的模型在系统中是否可行， 这些金属簇参与电子转移途径。 由于金属蛋白质的复杂性质，电子鉴定 交换对生物功能的影响需要一些先验知识， 人们可能观察到的可能影响。这类信息完全是 这是文献中所缺乏的。因此，本文所述的研究重点是 合成定制的分子，其中所有方面的电子和 分子结构在实验控制之下。这项研究代表了一个 合成无机和物理-无机化学物质的混合物，其中 合成与详细的光谱研究相结合， 飞秒时间分辨电子探针的吸收测量 转移分子间和分子内电子转移都在研究中。 模型复合物含有氧桥二铁（III）核心，以及 双中心铁硫簇合物制备分子，其中， 系统地介绍了交换耦合（用变温 磁性测量）。电子转移动力学，然后监测使用 各种静态和时间分辨光谱（例如，吸收，发射， 振动）。分子间研究采取经典的形式， Stern-Volmer型猝灭研究，而分子内动力学是 通过采用共价连接的合成定制系统进行探测， 电子供体和受体。据信，确定是否 电子交换可以在电子转移过程中起作用 将代表着理解电子的重要概念性的一步 一般的转移反应，以及贷款的具体见解， 多核金属簇在含过渡金属蛋白中的作用。