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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Q(y) and Q(x) Absorption Bands for Bacteriochlorophyll a Molecules from LH2 and LH3
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Q(y) and Q(x) Absorption Bands for Bacteriochlorophyll a Molecules from LH2 and LH3

机译：Q（y）和Q（x）用于精能氯苯基的吸收带，来自LH2和LH3的分子

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摘要

Light-harvesting systems 2 and 3 (LH2 and LH3) act as antennas for the initial light capture by photosynthetic purple bacteria, thus initiating the conversion of solar energy into chemical energy. The main absorbers are carotenoids and bacteriochlorophylls (BChls), which harvest different parts of the solar spectrum. The first two optical transitions in BChl produce the Q(y) and Q(x) absorption bands. The large size of BChl molecules has prevented accurate computational determination of the electronic structures for the relevant states, until we recently succeeded in obtaining the excitation energies and transition dipole moments of the first (Q(y)) transition for all BChls in LH2 and LH3 using multi-state multiconfigurational second-order perturbation theory calculations. In this work, we go one step further, compute the corresponding values for the Q(x), transition, in line with previous work [J. Am. Chem. Soc. 2017, 139, 7558-7567], and compare and assess our data against excitation energies obtained through time dependent density functional theory methods. Interestingly, we find that the two transitions respond differently to BChls' geometrical factors, such as the macrocycle ring curvature and the dihedral torsion of the acetyl moiety. These findings will aid the unraveling of structure-function relationships for absorption and energy transfer processes in purple bacteria, and once again this demonstrates the viability of multireference quantum chemical methods as computational tools for the photophysics of biomolecules.
机译：光收获系统2和3（LH2和LH3）作为光合紫色细菌的初始光线捕获的天线，从而将太阳能转化为化学能。主要吸收剂是类胡萝卜素和菌脑（BCHL），其收获太阳光谱的不同部分。 BCHL中的前两个光学转换产生Q（Y）和Q（X）吸收带。大尺寸的BCHL分子防止了相关状态的电子结构的准确计算确定，直到我们最近成功地获得了LH2和LH3中所有BCHL的第一（Q（Y））转变的激励能量和转变偶极矩使用多态多功能术二阶扰动理论计算。在这项工作中，我们进一步走了一步，计算Q（x）的相应值，转换，符合先前的工作[J.是。化学。 SOC。 2017,139,7558-7567]，并比较并评估我们通过时间依赖性函数理论方法获得的励磁能量的数据。有趣的是，我们发现这两个转变对BCHLS的几何因子不同，例如宏观环曲率和乙酰基的二偏摩托。这些发现将有助于解开紫色细菌中的吸收和能量转移过程的结构功能关系，并且再次表现出多引导量子化学方法作为生物分子的光学学学的计算工具的可行性。

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