VIBRATIONAL STUDIES OF ENERGY TRANSDUCING PROTEINS

拟议研究的具体目标是表征 光物理的结构、振动和电子特性 活性细菌叶绿素 (BChl) 和细菌脱镁叶绿素 (BPh) 辅因子 细菌光合反应中心（RC）。 选择细菌 RC 用于研究，因为此类蛋白质代表了原型模型 研究介导电荷分离的因素的系统 生物膜。 细菌 RC 用于检查这一点的效用 该过程是由于以下事实：（1）高分辨率X射线晶体学 数据可用于多个物种的 RC 和 (2) 基因工程 对于其中某些物种来说，技术已经很成熟。 这两个 任何哺乳动物膜结合蛋白均不满足标准 参与初级电荷分离和能量转换过程。 该研究的主要研究工具是共振拉曼 (RR) 光谱学。 第一个主要目标是表征属性 转基因 RC 中的 BChl/BPh 辅因子具有新颖性 电子转移特性。 这些研究将集中于一系列 Rb、荚膜的突变体，其中氨基酸已被替换 与附件 BChl 和 BPh 非常接近的残基 蛋白质电子转移活性 L 分支上的辅助因子。 的 转基因 RC 将包括突变体，其中电子转移 已首先被记录为沿着通常不活动的 M 分支进行 蛋白质。 在所有情况下，RR 研究都将在 RC 软管上进行 详细的电子转移动力学已通过时间分辨得到阐明 光学实验。 第二个主要目标是进行 RR 研究 旨在确定低频振动性质的RC BChl/BPh 辅助因子的模式与最低的强耦合 能量光学跃迁。 这些研究的主要目标是 主要电子供体。 低频模式的表征 将通过采集和分析 RC 的 RR 数据来进行标记 15N、26Mg 和 15N/26Mg。 所有研究的长期目标是 确定辅因子（结构、 电子密度分布、电子声子耦合）控制和/或 反映它们的功能特征（电子转移和电荷 穿过生物膜的分离）。

The specific aims of the proposed research are to characterize the structural, vibronic, and electronic properties of the photophysically active bacteriochlorophyll (BChl) and bacteriopheophytin (BPh) cofactors in bacterial photosynthetic reaction centers (RCs). Bacterial RCs were chosen for study because of this class of proteins represents a prototypical model system for investigating the factors which mediate charge separation across a biological membrane. The utility of bacterial RCs for examining this process is due to the fact that (1) high-resolution X-ray crystallographic data are available for RCs from several species and (2) genetic engineering techniques are well developed for certain of these species. These two criteria are not satisfied for any mammalian membrane-bound proteins involved in primary charge-separation and energy-transduction processes. The principal investigative tool for the studies is resonance Raman (RR) spectroscopy. The first major objective is to characterize the properties of the BChl/BPh cofactors in genetically modified RCs which exhibit novel electron-transfer properties. These studies will focus on a series of mutants of Rb, capsulatus wherein replacements have been made in amino acid residues which are in close proximity to the accessory BChl and BPh cofactors on the electron-transfer active L branch of the protein. The genetically modified RCs will include mutants in which electron transfer has been first documented to proceed down the normally inactive M branch of the protein. In all cases the RR studies will be conducted on RCs hose detailed electron-transfer kinetics have been elucidated via time-resolved optical experiments. The second major objective is to conduct RR studies on RCs aimed at determining the nature of the low-frequency vibrational modes of athe BChl/BPh cofactors which are strongly coupled to the lowest- energy optical transition(s). The principal target of these studies is the primary electron donor. The characterization of the low-frequency modes will proceed via acquisition and analysis of RR data from RCs labeled with 15N, 26Mg, and 15N/26Mg. The long-term objective of all the studies is to determine how the physical properties of the cofactors (structure, electron-density distribution, electron-phonon coupling) govern and/or reflect their functional characteristics (electron transfer and charge separation across the biological membrane).