ELECTRON AND PROTON TRANSFER IN REACTION CENTERS

电子和质子转移的控制因素 细菌光合作用反应中心(RC)的研究。注册局是 最具特性的膜内电子转移蛋白 通过耦合电子和电子在细胞中储存化学渗透能 质子转移。实验与理论的结合 这些方法将被用来理解协同因素之间的相互作用 和蛋白质规定了辅因子亲和力的相关性质 AM电化学中的结合位置，以及周围残基的pKa。 将使用经典的静电学计算来分析 不同氧化还原辅因子的电化学中点(E-m‘s) RCS。RC活动侧和非活动侧的E-M将计算为 确定电子转移是否会受到德尔塔G差异的限制。 光学测量闪光引发的电子转移将放置 二次对苯二酚电荷复合速率的限制 沿着蛋白质不活跃的那一边。对苯二酚和苯二酚的改性 结合位置将决定该反应是否受局部效应的限制 或者是通过中间的蛋白质。对于RCS中的两个苯二酚结合位点， 用静电学方法得到控制电磁参数的因素图 计算结果将与对苯二酚的详细计算进行比较 网站的半喹酮亲和力。这一分析将补充 丰富的测得结合常数和Em的数据库。 具有不同电荷分布的喹酮类化合物将被表征 从实验和理论上都是如此。波尔兹曼分布 用蒙特卡罗方法可以得到RCS中不同的质子态 不同电离态的静电能采样 测定残留物pKas。不同氧化还原状态下的PKA位移将显示 与电子转移相耦合的质子吸收途径。这个 极性质子对计算的pKa和E-m的摄动 本课程将探讨与电子转移有关的运动。这将是 辅以对温度依赖关系的实验测量 (BCHL)2+BPH-和(BCHL)2+QA-之间的增量G (BCHL)2+BPh-在ns上产生实质性驰豫的过程 对S来说，时间尺度是可以冻结和刻画的。

The factors controlling delta Gs of electron and proton transfers in the bacterial photosynthetic reaction center (RC) will be studied. The RC is the best characterized of the intramembrane election transfer proteins that store chemiosmotic energy in the cell by coupling electron and proton transfers. A combination of experimental and theoretical approaches will be used to understand how interactions between cofactors and protein specify the related properties of cofactor affinity for a binding site, in AM electrochemistry, and pKa's of surrounding residues. Classical electrostatics calculations will be used to analyze electrochemical midpoints (E-m's) of the different redox cofactors in RCs. E-m's of active and inactive sides of the RC will be calculated to determine if electron transfer could be limited by delta G differences. Optical measurement of flash initiated electron transfer will place limits on the rate of charge recombination from the secondary quinone along the inactive side of the protein. Modification of the quinone and binding site will determine if this reaction is limited by local effects or by the intervening protein. For the two quinone binding sites in RCs, the picture of factors controlling E-m's obtained by electrostatics calculations will be compared with detailed calculations of quinone and semiquinone affinities for the site. This analysis will complement a rich data base of measured binding constants and Em's. The function of quinones with different charge distributions will be characterized experimentally and theoretically. The Boltzmann distribution of different protonation states in RCs will be obtained by Monte Carlo sampling of the electrostatic energies of different ionization states to determine residue pKas. pKa shifts in different redox states will show the pathway of proton uptake that is coupled to electron transfer. The perturbation of calculated pKa's and E-m's because of polar proton motions coupled to electron transfer will be explored. This will be complemented by experimental measurement of the temperature dependence of the delta G between (BChl)2+BPh- and (BChl)2+QA- to investigate if the processes that yield the substantial relaxation of (BChl)2+BPh- on the ns to mu s time scale can be frozen out and characterized.