REACTION CENTER DYNAMICS

我们正在使用光学和红外光谱来研究 生物体的能量传递机制。作为一名 模型系统，我们关注的是光诱导的电子传输 细菌反应中心(RC)的反应。这个积分 膜蛋白启动光诱导的电子传递 细菌光合作用的反应。我们感兴趣的是 检测电子传递中的新反应中间体 用物理化学对这些事件进行排序和解释 模特们。力量的分子本质决定了 它的光谱、动力学和热力学特征 蛋白质将被测定。 将使用动力学荧光光谱技术来监测 反应中间产物的增量G度的松弛 电子转移序列。特定的氨基酸和蛋白质 亚基可能在这些事件中发挥作用；这一假设将是 通过检查现场定向修改的RC的功能进行测试 突变。 通过改变L分支谷氨酸-104点或附近的氨基酸，我们 希望了解静电氢键是如何 相互作用决定了反常的基态电子和 BPhL的氧化还原性质。在还原状态下，一种蛋白质 (溶剂)重排或互变异构化可能很重要 对于BPhL的氧化还原平衡活性。这一假说将 接受测试。类似的考虑也适用于第一对苯二酚。 电子受体，QA。保守的(非极性)突变 与假体组相邻的部位可能会扰乱现有的 蛋白质-假体基团相互作用足以引起 P+QA-态自由能的可测量变化。 蛋白质的作用也可能被假定为在 电子传输。蛋白质原子可能以振动方式偶联到 电子转移。溶剂-蛋白质偶极波动可能起到 在某些条件下起到限速作用。也有可能是 蛋白质催化的光合色素互变异构化 可能与限速步骤中的电子传输有关。通过 测量突变如何改变电子传输的动态 通过时间分辨的吸光度和荧光变化，我们 希望建立一幅关于原子核运动是如何与 反应中心蛋白质中的电子转移。 定点突变也将对丰富的信息有用 RC中的光谱指认(核磁共振、红外、能谱、拉曼) 蛋白。

We are using optical and infrared spectroscopy to study the mechanism of energy transduction by living organisms. As a model system, we are focusing on light-induced electron transport reactions in the bacterial reaction center (RC). This integral membrane protein initiates the light-induced electron transport reaction of bacterial photosynthesis. We are interested in detecting novel reaction intermediates in the electron transport sequence and interpreting these events with physical chemical models. The molecular nature of the forces that determine the spectroscopic, kinetic and thermodynamic characteristics of this protein will be determined. Kinetic fluorescence spectroscopy will be used to monitor relaxations in delta G degrees of reaction intermediates in the electron transfer sequence. Specific amino acids and protein subunits may play a role in these events; this hypothesis will be tested by examining function of RC's modified by site directed mutations. By altering amino acids at or near L branch glutamic acid-104, we hope to understand how electrostatic hydrogen-bonding interactions determine the unusual ground state electronic and redox properties of BPhL. In the reduced state, a protein (solvent) rearrangement or tautomerization could be important for the redox equilibrium activity of BPhL. This hypothesis will be tested. Similar considerations apply to the first quinone electron acceptor, QA. Conservative (nonpolar) mutations at sites adjacent to the prosthetic group may perturb the existing protein-prosthetic group interactions sufficiently to cause measurable changes in the free energy of the state P+QA-. A role for protein may also be postulated in the dynamics of electron transport. Protein atoms may be vibronically coupled to electron transfer. Solvent-protein dipolar fluctuations may play a rate-limiting role under some conditions. It is also possible that protein-catalyzed tautomerization of the photosynthetic pigments could be linked to electron transport at a rate-limiting step. By measuring how mutations alter the dynamics of electron transport through time-resolve absorbance and fluorescence changes, we hope to build a picture of how nuclear motions are coupled to electron transfer in the reaction center protein. Site directed mutations will also be useful for information-rich spectroscopic assignments (NMR, IR, ENDOR, Raman) in the RC protein.