Beekman L M, Visschers R W, Monshouwer R, Heer-Dawson M, Mattioli T A, McGlynn P, Hunter C N, Robert B, van Stokkum I H, van Grondelle R
Department of Physics and Astronomy, Free University of Amsterdam, The Netherlands.
Biochemistry. 1995 Nov 14;34(45):14712-21. doi: 10.1021/bi00045a012.
The spectroscopic analysis of the antenna-deficient Rhodobacter sphaeroides strain RCO1 has been extended to an investigation of the kinetics and spectroscopy of primary charge separation. Global analysis of time-resolved difference spectra demonstrated that the rate of charge separation in membrane-bound reaction centers is slightly slower than in detergent-solubilized reaction centers from the same strain. A kinetic analysis of the decay of the primary donor excited state at single wavelengths was carried out using a high repetition rate laser system, with the reaction centers being maintained in the open state using a combination of phenazine methosulfate and horse heart cytochrome c. The kinetics of primary charge separation in both membrane-bound and solubilized reaction centers were found to be non-monoexponential, with two exponential decay components required for a satisfactory description of the decay of the primary donor excited state. The overall rate of charge separation in membrane-bound reaction centers was slowed if the primary acceptor quinone was reduced using sodium ascorbate. This slowing was caused, in part, by an increase in the relative amplitude of the slower of the two exponential components. The acceleration in the rate of charge separation observed on removal of the reaction center from the membrane did not appear to be caused by a significant change in the electrochemical properties of the primary donor. The influence of the environment of the reaction center on primary charge separation is discussed together with the origins of the non-monoexponential decay of the primary donor excited state.
对缺乏天线的球形红细菌菌株RCO1的光谱分析已扩展到对初级电荷分离动力学和光谱学的研究。对时间分辨差分光谱的全局分析表明，膜结合反应中心中的电荷分离速率略慢于来自同一菌株的去污剂溶解的反应中心。使用高重复率激光系统对单波长下初级供体激发态的衰减进行了动力学分析，通过硫酸甲酯吩嗪和马心细胞色素c的组合使反应中心保持在开放状态。发现膜结合和溶解的反应中心中初级电荷分离的动力学均非单指数，需要两个指数衰减分量才能令人满意地描述初级供体激发态的衰减。如果使用抗坏血酸钠还原初级受体醌，则膜结合反应中心中的电荷分离总速率会减慢。这种减慢部分是由两个指数分量中较慢的那个的相对幅度增加引起的。从膜上去除反应中心时观察到的电荷分离速率的加速似乎不是由初级供体的电化学性质的显著变化引起的。讨论了反应中心环境对初级电荷分离的影响以及初级供体激发态非单指数衰减的起源。
