Excitation transfer connectivity in different purple bacteria: A theoretical and experimental study
Excitation transfer connectivity in different purple bacteria: A theoretical and experimental study
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DOI：
10.1016/j.bbabio.2010.07.011
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发表时间：
2010-11-01
影响因子：
4.3
通讯作者：
Lavergne, Jerome
中科院分区：
文献类型：
--
作者：
de Rivoyre, Matthieu;Ginet, Nicolas;Lavergne, Jerome
光合膜容纳密集的光收集复合物，吸收光并将激发传递到反应中心（RC）。荧光产率（phi）和封闭RC的分数(x)之间的关系是关于激发到达封闭RC被重定向到另一个RC的概率的信息。在这项工作中，我们在这方面检查了来自各种细菌的膜，并从原子力或电子显微镜中寻找与光收集复合物排列的相关性。论文的第一部分致力于理论研究，分析各种模型中的phi(x)关系：单体或二聚体RC-LH1核心配合物，有或没有外围LH2配合物。我们表明，这里使用的简单的“均匀”动力学处理与更详细的主方程计算很好地吻合。我们还讨论了本技术所得信息与单重态湮灭实验所得信息的一致性。实验结果表明，由于封闭单元的激励转移，开放rc的截面增强随种类的不同而变化在1.5 ~ 3之间。堆芯传输速率（包括通过LH2的间接途径）与开放单元中捕获速率的比值在0.5到4之间。它在球形红杆菌中约为1，在缺乏LH2的突变体中没有显著增加，尽管在这种情况下，二聚体核心复合物之间的接触次数更多。这种细菌的连通性在很大程度上是由于二聚体（RC-LH1-PufX）(2)复合物的两个伙伴之间的快速转移。然而，在不含类胡萝卜素和不含lh2的菌株R26中，连通性增加，我们将其归因于异常的LH1。在Rhodospirillum photometricum中发现了相对较高的连通性，尽管没有Fassioli et al.（2010）计算中预测的那么高。这说明了磁芯到磁芯激励传递的测量效率与理论估计之间存在更普遍的差异。我们认为，在紫色细菌中发现的有限核心到核心的连通性可能反映了光收集效率和醌扩散的阻碍之间的权衡，这将导致过于紧密的LH配合物。(C) 2010 Elsevier B.V.版权所有
Photosynthetic membranes accommodate densely packed light-harvesting complexes which absorb light and convey excitation to the reaction center (RC). The relationship between the fluorescence yield (phi) and the fraction (x) of closed RCs is informative about the probability for an excitation reaching a closed RC to be redirected to another RC. In this work, we have examined in this respect membranes from various bacteria and searched for a correlation with the arrangement of the light-harvesting complexes as known from atomic force or electron microscopies. A first part of the paper is devoted to a theoretical study analyzing the phi(x) relationship in various models: monomeric or dimeric RC-LH1 core complexes, with or without the peripheral LH2 complexes. We show that the simple "homogeneous" kinetic treatment used here agrees well with more detailed master equation calculations. We also discuss the agreement between information derived from the present technique and from singlet annihilation experiments. The experimental results show that the enhancement of the cross section of open RCs due to excitation transfer from closed units varies from 1.5 to 3 depending on species. The ratio of the core to core transfer rate (including the indirect pathway via LH2) to the rate of trapping in open units is in the range of 0.5 to 4. It is about 1 in Rhodobacter sphaeroides and does not increase significantly in mutants lacking LH2 despite the more numerous contacts between the dimeric core complexes expected in this case. The connectivity in this bacterium is due in good part to the fast transfer between the two partners of the dimeric (RC-LH1-PufX)(2) complex. The connectivity is however increased in the carotenoidless and LH2-less strain R26, which we ascribe to an anomalous LH1. A relatively high connectivity was found in Rhodospirillum photometricum, although not as high as predicted in the calculations of Fassioli et al. (2010). This illustrates a more general discrepancy between the measured efficiency of core to core excitation transfer and theoretical estimates. We argue that the limited core to core connectivity found in purple bacteria may reflect a trade-off between light-harvesting efficiency and the hindrance to quinone diffusion that would result from too tightly packed LH complexes. (C) 2010 Elsevier B.V. All rights reserved.