Effects of applied electric fields on the quantum yields of the initial electron-transfer steps in bacterial photosynthesis. 1. Quantum yield failure
Effects of applied electric fields on the quantum yields of the initial electron-transfer steps in bacterial photosynthesis. 1. Quantum yield failure
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施加电场对细菌光合作用初始电子转移步骤量子产率的影响。
DOI：
10.1021/j100152a022
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发表时间：
1993
期刊：
影响因子：
--
通讯作者：
S. Boxer
中科院分区：
文献类型：
--
作者：
K. Lao;S. Franzen;R. Stanley;D. Lambright;S. Boxer
测量了外加电场对非取向 Rb 的 P[sup +]H[sup [minus]]、P[sup +]Q[sub A][sup [minus]] 和 [sup 3]P 态形成的量子产率的影响。聚乙烯醇 (PVA) 薄膜和甘油缓冲玻璃中的球状反应中心在 80 K 下。对于数据重叠的两种介质中的所有三个可观测量，场依赖性的形状和大小都非常相似。这一结果表明量子产率的降低发生在电荷分离过程的早期步骤。在 PVA 薄膜中，在 2.5 x 10[sup 6] V/cm 的场强下观察到量子产率降低了 50% 以上。可能的机制包括 [sup 1]P 的场依赖性非辐射衰变、P[sup +]B[sup [minus]] 的场依赖性形成或衰变速率（如果 P[sup +]B[sup [minus]] 很重要），以及 P[sup +]H[sup [minus]] 的非松弛形式的场依赖性形成或衰变。观察到小电场效应对自由基对 P[sup +]H[sup [minus]] 的复合率和 [sup 3]P 量子产率的磁场依赖性。这可能是因为那些在电场中幸存下来并成为 P[sup +]H[sup [minus]] 和 [sup 3]P 的反应中心定向子群是那些在早期没有经历量子产率失败的子群。场诱导效应为通过跨膜电位调节光合电荷分离的可能机制提供了基础。 55 条参考文献，5 个图。« 更少
The effect of an applied electric field has been measured for the quantum yield of formation of the P[sup +]H[sup [minus]], P[sup +]Q[sub A][sup [minus]], and [sup 3]P states of nonoriented Rb. sphaeroides reaction centers at 80 K in poly(vinyl alcohol) (PVA) films and in glycerol-buffer glasses. Both the shape and magnitude of the field dependence are very similar for all three observables in both media where the data overlap. This result suggests that the reduction of the quantum yield occurs at a very early step in the charge separation process. More than 50% reduction in the quantum yield is observed at fields of 2.5 x 10[sup 6] V/cm in PVA films. Possible mechanisms include field-dependent nonradiative decay of [sup 1]P, a field-dependent rate of formation or decay of P[sup +]B[sup [minus]] if P[sup +]B[sup [minus]] is important, and field-dependent formation or decay of an unrelaxed form of P[sup +]H[sup [minus]]. Small electric field effects are observed on the recombination rate of the radical pair P[sup +]H[sup [minus]] and the magnetic field dependence of the [sup 3]P quantum yield. This is likely because those orientational subpopulations of reaction centers which survive to become P[sup +]H[sup [minus]] and [sup 3]P inmore » an electric field are those which did not experience quantum yield failure at an early step. The field-induced effects provide a basis for a possible mechanism to regulate photosynthetic charge separation by transmembrane potentials. 55 refs., 5 figs.« less