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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Charge separation is virtually irreversible in photosystem II core complexes with oxidized primary quinone acceptor
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Charge separation is virtually irreversible in photosystem II core complexes with oxidized primary quinone acceptor

机译：在带有氧化伯醌受体的光系统II核心配合物中，电荷分离实际上是不可逆的

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摘要

X-ray structures of the Photosystem II (PSII) core revealed relatively large interpigment distances between the CP43 and CP47 antenna complexes and the reaction center (RC) with respect to the interpigment distances in a single unit. This finding questions the possibility of fast energy equilibration among the antenna and the RC, which has been the basic explanation for the measured PSII fluorescence kinetics for more than two decades. In this study, we present time-resolved fluorescence measurements obtained with a streak-camera setup on PSII core complexes from Thermosynechococcus elongatus at room temperature (RT) and at 77 K. Kinetic modeling of the RT data obtained with oxidized quinone acceptor QA, reveals that the kinetics are best described by fast primary charge separation at a time scale of 1.5 ps and slow energy transfer from the antenna into the RC, which results in an energy equilibration time between the antenna and the RC of about 44 ps. This model is consistent with structure-based computations. Primary radical pair formation was found to be a virtually irreversible process. Energy equilibration within the CP43 and CP47 complexes is shown to occur at a time scale of 8 ps. Kinetic modeling of the 77 K data reveals similar energy transfer time scales in the antenna units and among the antenna and the RC as at RT, respectively, 7 and 37 ps. We conclude that the energy transfer from the CP43/CP47 antenna to the RC is the dominant factor in the total charge separation kinetics in intact PSII cores.
机译：Photosystem II（PSII）核心的X射线结构显示，相对于单个单元中的颜料间距离，CP43和CP47天线配合物与反应中心（RC）之间的颜料间距离相对较大。这个发现对天线和RC之间快速能量平衡的可能性提出了质疑，这已经是二十多年来对PSII荧光动力学测量的基本解释。在这项研究中，我们介绍了在室温（RT）和77 K下，用条纹相机对伸长的嗜热嗜热球菌的PSII核配合物进行的时间分辨荧光测量。通过氧化醌受体QA获得的RT数据的动力学模型揭示了通过在1.5 ps的时间尺度上进行快速一次电荷分离和从天线到RC的缓慢能量转移，可以最好地描述动力学，这导致天线和RC之间的能量平衡时间约为44 ps。该模型与基于结构的计算一致。发现初级自由基对的形成实际上是不可逆的过程。 CP43和CP47配合物中的能量平衡显示为8 ps的时间尺度。 77 K数据的动力学建模表明，在RT处，天线单元中以及天线与RC之间的能量传递时间尺度分别为7 ps和37 ps，这两者相似。我们得出的结论是，从CP43 / CP47天线到RC的能量转移是完整PSII磁芯中总电荷分离动力学的主要因素。

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