Department of Chemistry and Center for Photochemical Sciences, Bowling Green State University, Bowling Green, OH 43403, USA.
Phys Chem Chem Phys. 2013 Apr 21;15(15):5636-47. doi: 10.1039/c3cp43582b.
Light harvesting by LH1 and LH2 antenna proteins in the photosynthetic membranes of purple bacteria has been extensively studied in recent years for the fundamental understanding of the energy transfer dynamics and mechanism. Here we report the inhomogeneous structural organization of the LH2 complexes in photosynthetic membranes, giving evidence for the existence of energetically coupled linear LH2 aggregates in the native photosynthetic membranes of purple bacteria. Focusing on systematic model analyses, we combined AFM imaging and spectroscopic analysis with energetic coupling model analysis to characterize the inhomogeneous linear aggregation of LH2. Our AFM imaging results reveal that the LH2 complexes form linear aggregates with the monomer number varying from one to eight and each monomer tilted along the aggregated structure in photosynthetic membranes. The spectroscopic results support the attribution of aggregated LH2 complexes in the photosynthetic membranes, and the model calculation values for the absorption, emission and lifetime are consistent with the experimentally determined spectroscopic values, further proving a molecular-level understanding of the energetic coupling and energy transfer among the LH2 complexes in the photosynthetic membranes.
近年来，人们对光合细菌中 LH1 和 LH2 天线蛋白的光能捕获进行了广泛研究，以期深入了解能量转移动力学和机制。本文报道了光合膜中 LH2 复合物的不均匀结构组织，为天然光合细菌中存在能量耦合的线性 LH2 聚集体提供了证据。本文通过聚焦系统模型分析，将 AFM 成像与光谱分析与能量耦合模型分析相结合，对 LH2 的不均匀线性聚集进行了表征。AFM 成像结果表明，LH2 复合物在光合膜中形成了具有从一个到八个单体的线性聚集体，并且每个单体沿着聚合结构倾斜。光谱结果支持在光合膜中存在聚集的 LH2 复合物，并且吸收、发射和寿命的模型计算值与实验确定的光谱值一致，这进一步证明了对光合膜中 LH2 复合物之间能量耦合和能量转移的分子水平理解。
