Structure and Dynamics of Radical Intermediates in Biological Electron Transfer Reactions

在这个由化学学部化学结构、动力学和机理b项目资助的项目中，加州大学圣地亚哥分校的朱迪·金教授正在研究生物系统中的电荷流动。蛋白质分离电荷的能力对自然界的许多化学过程都很重要，包括光合作用和呼吸作用。她的研究小组利用光学工具结合分子生物学方法来研究两种模型系统中与电子流相关的蛋白质结构和速率。这个项目的结果不仅阐明了大自然是如何控制长距离电荷流动的，而且这些发现也与其他学科有关，如生物学和物理学。这项研究的广泛影响是重要的，因为这里描述的发现可能会激发人造和仿生设备中远程电子流定向控制的新策略。除了实验室工作，研究团队还参与了一些外展项目，以加强STEM主题对K-12学生的重要性。本项目主要研究蛋白质中参与电子转移（ET）反应的氨基酸。现代光谱技术被用来表征蛋白质中的色氨酸和酪氨酸自由基，并将蛋白质环境与自由基反应性联系起来。研究的重点是：(1)生物色氨酸和酪氨酸自由基的光学、磁性和电子性质；(2)氨基酸自由基ET反应的动力学和结构变化；(3)氢键和局部介质对自由基稳定性和动力学的影响；(4)沿蛋白质氨基酸链的多步ET反应。采用光谱技术，包括时间分辨和稳态共振拉曼，瞬态吸收和电子顺磁共振波谱。这些工具，结合蛋白质诱变的努力，提供了对阳离子和中性自由基物种的结构和动力学的见解。

In this project funded by the Chemical Structure, Dynamics, and Mechanisms-B program of the Chemistry Division, Professor Judy Kim of the University of California at San Diego is investigating the flow of charge in biological systems. This ability of proteins to separate charge is important for many chemical processes in nature, including photosynthesis and respiration. Her research group utilizes optical tools combined with molecular biology methods to investigate protein structures and rates associated with the flow of electrons in two model systems. Results from this project not only elucidate how nature controls the flow of charge over long distances, but these findings are also relevant to other disciplines, such as biology and physics. The broader impact of the research is significant because discoveries described here may inspire new strategies for directional control of long-range electron flow in man-made and biomimetic devices. In addition to the laboratory efforts, the research team participates in outreach programs that reinforce the significance of STEM topics to K-12 students. This project focuses on amino acids that participate in electron transfer (ET) reactions in proteins. Modern spectroscopic techniques are used to characterize tryptophan and tyrosine radicals in proteins, and to correlate protein environment with radical reactivity. Key topics of investigation are (1) the optical, magnetic, and electronic properties of biological tryptophan and tyrosine radicals; (2) kinetics and structural changes associated with ET reactions of amino acid radicals; (3) effects of hydrogen-bonding and local dielectric on radical stability and dynamics; and (4) multi-step ET reactions along amino acid chains in a protein. Spectroscopic techniques are employed, including time-resolved and steady-state resonance Raman, transient absorption, and electron paramagnetic resonance spectroscopy. These tools, combined with protein mutagenesis efforts, provide insights on the structures and dynamics of the cation and neutral radical species.