Explaining Spectral Asymmetries and Excitonic Characters of the Core Pigment Pairs in the Bacterial Reaction Center Using a Screened Range-Separated Hybrid Functional
Explaining Spectral Asymmetries and Excitonic Characters of the Core Pigment Pairs in the Bacterial Reaction Center Using a Screened Range-Separated Hybrid Functional
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DOI：
10.1021/acs.jpcb.9b07646
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发表时间：
2019-10-24
影响因子：
3.3
通讯作者：
Dunietz, Barry D.
中科院分区：
文献类型：
--
作者：
Aksu, Huseyin;Schubert, Alexander;Dunietz, Barry D.
计算研究了细菌反应中心（BRC）中特殊色素对（P）和相邻色素的光谱峰。我们采用了一种新的框架的基础上的极化一致的处理的电介质环境，结合极化连续模型（PCM）与时间相关的屏蔽距离分离的混合（SRSH）密度泛函理论。我们的计算定量再现最近测得的P激子状态和光谱不对称性的激发态的相邻的细菌叶绿素a（BChl）和bacteriopheophytin a（BPhe）的色素对之间的光谱峰分裂。对于特殊的对，之间的吸收态和蓝移半暗态的分裂能量为0.07 eV的发现与测量值接近一致。BChl和BPhe颜料的伪对称对内的光谱不对称性被解释为导致局部不同的有效介电环境中的A和B分支，其中后者暴露于较小的偏振环境。我们的分析基于X射线分辨结构，通过有效的介电环境来解决相邻颜料对电子结构的影响。我们发现，光谱趋势只再现使用偏振一致的框架的基础上筛选的范围分离的混合功能，而B3 LYP-PCM能量不能提供正确的趋势。
Spectral peaks of the special pair (P) and adjacent pigments in the bacterial reaction center (BRC) are investigated computationally. We employ a novel framework based on a polarization-consistent treatment of the dielectric environment, combining the polarizable continuum model (PCM) with time-dependent screened range-separated hybrid (SRSH) density functional theory. Our calculations quantitatively reproduce recently measured spectral peak splits between P excitonic states and spectral asymmetries within the pairs of excited states of the adjacent bacteriochlorophyll a (BChl) and bacteriopheophytin a (BPhe) pigments. For the special pair, a splitting energy between the absorptive state and a blue-shifted semidark state of 0.07 eV is found in close agreement with the measured value. The spectral asymmetries within the pseudosymmetric pairs of BChl and BPhe pigments are interpreted to result from locally different effective dielectric environments in the A and the B branch, where the latter are exposed to a lesser polarizing environment. We base our analysis on X-ray-resolved structures and where the effect of neighboring pigments on the electronic structure is addressed through an effective dielectric environment. We show that the spectral trends are only reproduced using a polarization-consistent framework based on a screened range-separated hybrid functional, whereas B3LYP-PCM energies fail to provide the correct trends.