Department of Physics, University of Michigan, Ann Arbor, MI, USA.
School of Molecular Sciences, Arizona State University, Tempe, AZ, USA.
Nat Commun. 2021 May 14;12(1):2801. doi: 10.1038/s41467-021-23060-9.
Photochemical reaction centers are the engines that drive photosynthesis. The reaction center from heliobacteria (HbRC) has been proposed to most closely resemble the common ancestor of photosynthetic reaction centers, motivating a detailed understanding of its structure-function relationship. The recent elucidation of the HbRC crystal structure motivates advanced spectroscopic studies of its excitonic structure and charge separation mechanism. We perform multispectral two-dimensional electronic spectroscopy of the HbRC and corresponding numerical simulations, resolving the electronic structure and testing and refining recent excitonic models. Through extensive examination of the kinetic data by lifetime density analysis and global target analysis, we reveal that charge separation proceeds via a single pathway in which the distinct A chlorophyll a pigment is the primary electron acceptor. In addition, we find strong delocalization of the charge separation intermediate. Our findings have general implications for the understanding of photosynthetic charge separation mechanisms, and how they might be tuned to achieve different functional goals.
光化学反应中心是驱动光合作用的引擎。来自嗜热菌的反应中心（HbRC）被认为最接近光合作用反应中心的共同祖先，这激发了人们对其结构-功能关系的深入理解。最近 HbRC 晶体结构的阐明激发了对其激子结构和电荷分离机制的先进光谱研究。我们对 HbRC 及其相应数值模拟进行了多光谱二维电子光谱学研究，解析了电子结构并测试和改进了最近的激子模型。通过寿命密度分析和全局目标分析对动力学数据进行广泛检查，我们揭示了电荷分离是通过一个单一的途径进行的，其中独特的 A 叶绿素 a 色素是主要的电子受体。此外，我们发现电荷分离中间体具有很强的离域性。我们的发现对理解光合作用电荷分离机制以及如何调整它们以实现不同的功能目标具有普遍意义。
