REACTION CENTER DYNAMICS

细菌反应中心蛋白（RC）是一种完整的膜 启动光驱动电子转移反应的蛋白质 光合作用 随着高分辨率晶体结构的出现， RC已经成为一种中心的生物物理学范式， 蛋白质的结构/功能关系。 广泛的 生物化学、光谱、结构和理论技术， 接受过关于驻地协调员制度的培训，以回答以下问题： 基本的生物学相关性：RC如何将电 电荷穿过具有单位量子产率的膜双层？ 的 对该机制的完整说明需要研究大量的 能量转移、电子转移、质子转移和构象 平衡反应 多学科方法可能会产生最大的 有意义的见解。 在这个提议中，注意力集中在最早的电子转移上， 发生在飞秒和皮秒时间尺度上的反应。 的 P.I.建议探讨以下具体的机制问题： 1)是什么解释了电子转移的单向性 一个准对称蛋白质结构的背景 2)顺序如何 来描述电子转移事件吗 特别是， β（L）的作用，单体细菌叶绿素？ 什么动能 对这些事件的描述是适当的：超交换，两步， RC的非均匀分布？ 有准备的人兴奋吗 在电子转移之前振动平衡的状态？ 什么其他 弛豫过程的类型是重要的机制？ 3)什么 是基态和激发态的分子决定因素 光谱和氧化还原性质？ 这种蛋白质是否起着积极的作用， 在机制中扮演被动角色？ 4)对这些的理论描述 过程是否合适？ 电子的非绝热理论 转移是否足够，还是需要其他形式主义？ 原则 这些研究所阐明的可能普遍适用 其他能量转换蛋白质。 私家侦探建议使用时间分辨和稳态光学 光谱技术来观察的形成和衰变 在野生型和选择的突变体RC中的中间体。 时间分辨 荧光和吸收实验将在广泛的范围内进行， 实验条件的范围。 全球动力学分析将是 应用于数据，以尝试一个公正的，可能是唯一的， 机械解释。 私家侦探还将修改 突变系统，并选择更多的RC突变体进行理化 分析. 在与其他人的合作下，突变结构将被 通过X射线晶体学测定，将获得ENDOR光谱，并且 将测量共振拉曼光谱。

The bacterial reaction center protein (RC) is an integral membrane protein that initiates the light-driven electron transfer reactions of photosynthesis. With the advent of a high-resolution crystal structure, the RC has emerged as a central biophysical paradigm for understanding structure/function relationships in proteins. A broad range of biochemical, spectroscopic, structural and theoretical techniques has been trained on the RC system, in an effort to answer a question of fundamental biological relevance: How does the RC separate electrical charges across a membrane bilayer with unitary quantum yield? The complete specification of the mechanism requires the study of a host of energy transfer, electron transfer, proton transfer and conformational equilibrium reactions. A multidisciplinary approach may yield the most meaningful insights. In this proposal, attention is focused on the earliest electron transfer reactions that occur on the femtosecond and picosecond time scales. The P.I. proposes to approach the following specific mechanistic questions: 1) What accounts for the unidirectionality of electron transfer in the context of a quasisymmetric protein structure? 2) How is the sequence of electron transfer events to be described? In particular, what is the role of Beta(L), the monomeric bacteriochlorophyll? What kinetic description of these events is appropriate: superexchange, two step, inhomogeneous distributions of RCs? Is the initially-prepared excited state vibrationally equilibrated prior to electron transfer? What other types of relaxation processes are important to the mechanism? 3) What are the molecular determinants of the ground state and excited state spectroscopic and redox properties? Does the protein play an active or passive role in the mechanism? 4) What theoretical description of these processes is appropriate? Is the nonadiabatic theory of electron transfer adequate or is some other formalism required? The principles that are to be elucidated by these studies may be generally applicable to other energy-transducing proteins. The P.I. proposes to use time-resolved and steady-state optical spectroscopic techniques to observe the formation and decay of intermediates in wild-type and selected mutant RCs. Time-resolved fluorescence and absorption experiment will be conducted over a wide- range of experimental conditions. Global kinetic analysis will be applied to the data in order to attempt an unbiased, possibly unique mechanistic interpretation. The P.I. will also make modifications to the mutagenesis system and select more RC mutants for physicochemical analysis. In collaboration with others, mutant structures will be determined by x-ray crystallography, ENDOR spectra will be obtained, and resonance Raman spectra will be measured.