van Stokkum I H, Beekman L M, Jones M R, van Brederode M E, van Grondelle R
Faculty of Physics and Astronomy, Vrije Universiteit, Amsterdam, The Netherlands.
Biochemistry. 1997 Sep 23;36(38):11360-8. doi: 10.1021/bi9707943.
Absorbance difference kinetics were measured on quinone-reduced membrane-bound wild type Rhodobacter sphaeroides reaction centers in the wavelength region from 690 to 1060 nm using 800 nm excitation. Global analysis of the data revealed five lifetimes of 0.18, 1.9, 5.1, and 22 ps and a long-lived component for the processes that underlie the spectral evolution of the system. The 0.18 ps component was ascribed to energy transfer from the excited state of the accessory bacteriochlorophyll (B*) to the primary donor (P*). The 1.9 ps component was associated with a state involving a BChl anion absorbing in the 1020 nm region. This led to the conclusion that primary electron transfer is best described by a model in which the electron is passed from P* to the acceptor bacteriopheophytin (HL) via the monomeric bacteriochlorophyll (BL), with the formation of the radical pair state . An analysis assuming partial direct charge separation from B* [Van Brederode, M. E., Jones, M. R., and Van Grondelle, R. (1997) Chem. Phys. Lett. 268, 143-149] was also consistent with the data. Within the framework of a five component model, the 5.1 and 22 ps lifetimes were associated with charge separation and relaxation of the radical pair state respectively, providing a description which adequately accounted for the complex kinetics of decay of P*. Alternatively, by assuming that the 5.1 and 22 ps components originate from a single component with a multi-exponential decay, a simpler analysis with only four components could be employed, resulting in only a small increase (7%) in the weighted root mean square error of the fit. In both descriptions part of the decay of P* proceeds with a lifetime of about 2 ps. The relative merits of these alternative descriptions of the primary events in light-driven electron transfer are discussed. Similar measurements on YM210H mutant reaction centers revealed four lifetimes of 0.2, 3.1, and 12 ps and a long-lived component. The 3.1 and 12 ps lifetimes are ascribed to multi-exponential decay of the P* state. The differences with the WT data are discussed.
在800nm激发光下，对醌还原的膜结合野生型球形红细菌反应中心在690至1060nm波长范围内进行吸光度差动力学测量。对数据的全局分析揭示了系统光谱演化背后过程的五个寿命，分别为0.18、1.9、5.1和22皮秒以及一个长寿命成分。0.18皮秒的成分归因于从辅助细菌叶绿素的激发态（B*）到初级供体（P*）的能量转移。1.9皮秒的成分与一个涉及在1020nm区域吸收的BChl阴离子的状态相关。这导致得出结论，初级电子转移最好用一个模型来描述，在该模型中，电子从P通过单体细菌叶绿素（BL）传递给受体细菌脱镁叶绿素（HL），形成自由基对状态。假设从B进行部分直接电荷分离的分析[Van Brederode, M. E., Jones, M. R., and Van Grondelle, R. (1997) Chem. Phys. Lett. 268, 143 - 149]也与数据一致。在五成分模型的框架内，5.1和22皮秒的寿命分别与自由基对状态的电荷分离和弛豫相关，提供了一个充分解释P衰变复杂动力学的描述。或者，假设5.1和22皮秒的成分源自具有多指数衰变的单个成分，可以采用仅四个成分的更简单分析，拟合的加权均方根误差仅小幅增加（7%）。在这两种描述中，P衰变的一部分具有约2皮秒的寿命。讨论了光驱动电子转移中这些初级事件的替代描述的相对优点。对YM210H突变体反应中心的类似测量揭示了四个寿命，分别为0.2、3.1和12皮秒以及一个长寿命成分。3.1和12皮秒的寿命归因于P*状态的多指数衰变。讨论了与野生型数据的差异。
