REACTION CENTER DYNAMICS

细菌反应中心蛋白(RC)是一个完整的膜 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已经成为理解的一个中心生物物理范例 蛋白质中的结构/功能关系。范围广泛的 生化、光谱、结构和理论技术已经 接受了关于RC系统的培训，以努力回答以下问题 基本生物学相关性：RC是如何分离电信号的 具有单位量子产额的膜双层上的电荷？这个 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。多学科的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 在飞秒和皮秒时间尺度上发生的反应。这个 P.I.建议探讨以下具体的机械性问题： 1)是什么解释了电子转移的单向性 准对称蛋白质结构的背景？2)序列是如何的 要描述的电子转移事件的多少？特别是，什么是 单体细菌叶绿素--β(L)的作用？什么动能 对这些事件的描述是恰当的：超级交易所，两步， RCS分布不均匀？最初准备好的是不是很兴奋 电子转移前的振动平衡态？还有什么 松弛过程的类型对机制是重要的吗？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？这种蛋白质起到的是活性还是 在机制中的被动作用？4)这些是什么理论描述 流程是否合适？是电子的非绝热理论 转移是足够的，还是需要一些其他的形式主义？《原则》 这些研究将阐明的可能是普遍适用的 到其他能量转导蛋白。 P.I.建议使用时间分辨和稳态光学 用光谱技术观察原子核的形成和衰变 野生型和突变型RCS的中间体。时间分辨率 荧光和吸收实验将在广泛的- 实验条件的范围。全球动力学分析将是 应用于数据，以便尝试不偏不倚、可能是唯一的 机械的解释。私家侦探还将对 建立诱变体系，筛选更多用于理化的RC突变体 分析。在与其他人的合作中，突变结构将被 由X射线结晶学确定，将获得Endor谱，以及 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.