纳秒光解中断菌紫质光循环：K-590-->BR-570 反应。
Nanosecond photolytic interruption of bacteriorhodopsin photocycle: K-590 --> BR-570 reaction.
机构信息
Department of Chemistry and Optical Science Center, University of Arizona, Tucson, Arizona 85721 USA.
出版信息
Biophys J. 1992 Jun;61(6):1630-7. doi: 10.1016/S0006-3495(92)81966-5.
The molecular processes comprising the room temperature bacteriorhodopsin (BR) photocycle are examined through the properties of the photo-induced reverse reaction, K-590 + hnu --> BR-570 (K --> BR). Two sequential pumping pulses, each of 10-ns duration, are used, respectively, to initiate the photocycle via the forward BR-570 + hnu --> K-590 (BR --> K) reaction (532 nm) and to photolytically interrupt the thermal BR photocycle after a 20-ns delay via K --> BR (620-700 nm). The ground-state BR-570 population, monitored by 633-nm absorption 200 mus after the photocycle begins, provides a quantitative measure of the efficiency with which K --> BR interrupts the photocycle to reform BR-570. The quantum yield (Phi) for K --> BR is found to be 1.6 +/- 0.1 times larger than that for BR --> K which, when compared to a Phi of 0.64 for BR --> K, suggests that Phi for K --> BR is approximately 1.0. The significance of such a high efficiency K --> BR reaction with respect to mechanistic descriptions of the BR photocycle is discussed.
通过光致反向反应 K-590 + hnu --> BR-570（K --> BR）的性质，研究了组成室温细菌视紫红质（BR）光循环的分子过程。分别使用两个持续时间为 10-ns 的连续泵浦脉冲，通过正向 BR-570 + hnu --> K-590（BR --> K）反应（532nm）启动光循环，并在 20-ns 延迟后通过 K --> BR（620-700nm）光解中断热 BR 光循环。通过在光循环开始后 200μs 用 633nm 吸收监测基态 BR-570 种群，定量测量 K --> BR 中断光循环以重新形成 BR-570 的效率。发现 K --> BR 的量子产率（Phi）比 BR --> K 的量子产率高 1.6 +/- 0.1 倍，与 BR --> K 的 Phi 值 0.64 相比，表明 K --> BR 的 Phi 值约为 1.0。讨论了这种高效 K --> BR 反应对于 BR 光循环机制描述的意义。
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