Kim Yongbin, Morozov Dmitry, Stadnytskyi Valentyn, Savikhin Sergei, Slipchenko Lyudmila V
Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907, United States.
Nanoscience Center and Department of Chemistry, University of Jyväskylä, P.O. Box 35, Jyväskylä 40014, Finland.
J Phys Chem Lett. 2020 Mar 5;11(5):1636-1643. doi: 10.1021/acs.jpclett.9b03486. Epub 2020 Feb 14.
High efficiency of light harvesting in photosynthetic pigment-protein complexes is governed by evolutionary-perfected protein-assisted tuning of individual pigment properties and interpigment interactions. Due to the large number of spectrally overlapping pigments in a typical photosynthetic complex, experimental methods often fail to unambiguously identify individual chromophore properties. Here, we report a first-principles-based modeling protocol capable of predicting properties of pigments in protein environment to a high precision. The technique was applied to successfully uncover electronic properties of the Fenna-Matthews-Olson (FMO) pigment-protein complex. Each of the three subunits of the FMO complex contains eight strongly coupled bacteriochlorophyll (BChl ) pigments. The excitonic structure of FMO can be described by an electronic Hamiltonian containing excitation (site) energies of BChl pigments and electronic couplings between them. Several such Hamiltonians have been developed in the past based on the information from various spectroscopic measurements of FMO; however, fine details of the excitonic structure and energy transfer in FMO, especially assignments of short-lived high-energy sites, remain elusive. Utilizing polarizable embedding quantum mechanics/molecular mechanics with the effective fragment potentials, we computed the electronic Hamiltonian of FMO that is in general agreement with previously reported empirical Hamiltonians and quantitatively reproduces experimental absorption and circular dichroism spectra of the FMO protein. The developed computational protocol is sufficiently simple and can be utilized for predictive modeling of other wild-type and mutated photosynthetic pigment-protein complexes.
光合色素 - 蛋白质复合物中高效的光捕获是由进化完善的蛋白质辅助调节单个色素特性和色素间相互作用来控制的。由于典型光合复合物中存在大量光谱重叠的色素，实验方法常常无法明确识别单个发色团的特性。在此，我们报告了一种基于第一性原理的建模方法，它能够高精度地预测蛋白质环境中色素的特性。该技术已成功应用于揭示费纳 - 马修斯 - 奥尔森（FMO）色素 - 蛋白质复合物的电子特性。FMO复合物的三个亚基中的每一个都包含八个强耦合的细菌叶绿素（BChl）色素。FMO的激子结构可以用一个电子哈密顿量来描述，该哈密顿量包含BChl色素的激发（位点）能量以及它们之间的电子耦合。过去基于FMO各种光谱测量信息已经开发了几个这样的哈密顿量；然而，FMO中激子结构和能量转移的精细细节，特别是短寿命高能位点的归属，仍然难以捉摸。利用带有有效片段势的可极化嵌入量子力学/分子力学，我们计算了FMO的电子哈密顿量，它与先前报道的经验哈密顿量总体上一致，并定量再现了FMO蛋白的实验吸收光谱和圆二色光谱。所开发的计算方法足够简单，可用于其他野生型和突变光合色素 - 蛋白质复合物的预测建模。
