School of Engineering and Science, Jacobs University Bremen, Campus Ring 1, 28759 Bremen, Germany.
J Phys Chem B. 2011 Feb 3;115(4):758-64. doi: 10.1021/jp1099514. Epub 2010 Dec 10.
The light absorption in light-harvesting complexes is performed by molecules such as chlorophyll, carotenoid, or bilin. Recent experimental findings in some of these complexes suggest the existence of long-lived coherences between the individual pigments at low temperatures. In this context, the question arises if the bath-induced fluctuations at different chromophores are spatially correlated or not. Here we investigate this question for the Fenna-Matthews-Olson (FMO) complex of Chlorobaculum tepidum by a combination of atomistic theories, i.e., classical molecular dynamics simulations and semiempirical quantum chemistry calculations. In these investigations at ambient temperatures, only weak correlations between the movements of the chromophores can be detected at the atomic level and none at the more coarse-grained level of site energies. The often-employed uncorrelated bath approximations indeed seem to be valid. Nevertheless, correlations between fluctuations in the electronic couplings between the pigments can be found. Depending on the level of theory employed, also correlations between the fluctuations of site energies and the fluctuations in electronic couplings are discernible.
在光捕获复合物中，光吸收是由叶绿素、类胡萝卜素或细菌叶绿素等分子来完成的。在这些复合物中的一些最近的实验发现表明，在低温下，各个色素之间存在长寿命相干性。在这种情况下，就会出现一个问题，即不同发色团之间的浴诱导波动是否存在空间相关性。在这里，我们通过组合原子理论，即经典分子动力学模拟和半经验量子化学计算，来研究绿硫菌科（Chlorobaculum tepidum）的 Fenna-Matthews-Olson (FMO) 复合物的这个问题。在环境温度下的这些研究中，只能在原子水平上检测到发色团运动之间的微弱相关性，而在更粗糙的位能水平上则没有。通常采用的不相关浴近似确实似乎是有效的。然而，可以发现色素之间电子耦合的波动之间存在相关性。根据所使用的理论水平，还可以发现位能波动和电子耦合波动之间的相关性。
