VIBRATIONAL STUDIES OF ENERGY TRANSDUCING PROTEINS

能量转换蛋白的振动研究

• 批准号: 2444679
• 负责人: DAVID F. BOCIAN
• 金额: $ 12.77万
• 依托单位: UNIVERSITY OF CALIFORNIA RIVERSIDE
• 依托单位国家: 美国
• 财政年份: 1988
• 资助国家: 美国
• 起止时间: 1988-07-01 至 2000-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2444679
• 关键词: Raman spectrometry; Rhodospirillales; bacterial pigment; biophysics; chemical bond resonance; chemical kinetics; chemical structure function; chlorophyll; cofactor; conformation; electric field; electron density; electron transport; electronic spectra; mutant; photochemistry; photosynthetic bacteria; photosynthetic reaction centers; reducing agents

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).

拟议研究的具体目标是描述 结构，振动，和电子性能的晶体 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（RCs）。 选择细菌RC 因为这类蛋白质代表了一个原型模型 用于研究介导电荷分离的因素的系统 一种生物膜 细菌RC用于检查这一点的实用性 这一过程是由于（1）高分辨率X射线晶体学 数据可用于几个物种的RC和（2）基因工程 对于这些物种中的某些，技术已经发展得很好。 这两 任何哺乳动物膜结合蛋白均不符合标准 参与初级电荷分离和能量转换过程。 研究的主要工具是共振拉曼（RR） 谱 第一个主要目标是表征 BChl/BPh辅因子在遗传修饰的RC中表现出新的 电子转移性质 这些研究将集中在一系列 其中在氨基酸中进行了替换的荚膜Rb突变体 与辅助BChl和BPh非常接近的残基 在蛋白质的电子转移活性L分支上的辅因子。 的 转基因RC将包括突变体，其中电子转移 已经首次记录为沿着通常不活动的M分支向下进行， 蛋白质。 在所有情况下，将对RC软管进行RR研究 详细的电子转移动力学已阐明通过时间分辨 光学实验 第二个主要目标是进行经常性资源研究 旨在确定低频振动的性质 BChl/BPh辅因子的模式，其与最低- 能量光学跃迁。 这些研究的主要目标是 主电子供体 低频模式的表征 将通过采集和分析标记为 15 N、26 Mg和15 N/26 Mg。 所有研究的长期目标是 确定辅因子的物理性质（结构， 电子密度分布、电子-声子耦合）控制和/或 反映它们的功能特性（电子转移和电荷 穿过生物膜的分离）。