Northwestern University, Department of Chemistry 2145 Sheridan Road, Evanston, Illinois, 60208-3113, USA.
J Chem Phys. 2011 Aug 21;135(7):075102. doi: 10.1063/1.3624376.
The capture and transduction of energy in biological systems is clearly necessary for life, and nature has evolved remarkable macromolecular entities to serve these purposes. The Fenna-Matthews-Olson (FMO) complex serves as an intermediate to transfer the energy from the chlorosome to the special pairs of different photo systems. Recent observations have both suggested the importance of coherent exciton transport within the FMO and motivated an elegant and appropriate theoretical construct for interpreting these observations. Here we employ a different approach to exciton transport in a relaxing environment, one based on the stochastic surrogate Hamiltonian method. With it, we calculate the quantum trajectories through the FMO complex both for the model involving seven bacteriochlorophylls that has been used before, and for one involving an eighth bacteriochlorophyll, which has been observed in some new and very important structural work. We find that in both systems, efficient energy transfer to the ultimate receptor occurs, but that because of the placement of, and energy relaxation among, the different bacteriochlorophyll subunits in the FMO complex, the importance of coherent oscillation that was discussed extensively for the seven site system is far less striking for the eight site system, effectively because of the weak mixing between the initial site and the remainder of the system. We suggest that the relevant spectral densities can be determinative for the energy transport route and may provide a new way to enhance energy transfer in artificial devices.
生物系统中能量的捕获和传递对于生命显然是必要的，大自然已经进化出了非凡的大分子实体来满足这些目的。Fenna-Matthews-Olson（FMO）复合物作为一种中间体，将能量从类菌叶绿素体转移到不同光系统的特殊对。最近的观察结果不仅表明了 FMO 中相干激子传输的重要性，而且为解释这些观察结果提供了一个优雅而合适的理论结构。在这里，我们采用一种不同的方法来研究在弛豫环境中的激子传输，这种方法基于随机替代哈密顿量方法。利用它，我们计算了 FMO 复合物中量子轨迹，既包括以前使用过的涉及七个细菌叶绿素的模型，也包括涉及第八个细菌叶绿素的模型，这个叶绿素在一些新的和非常重要的结构工作中被观察到。我们发现，在这两个系统中，有效的能量转移到最终受体都发生了，但由于 FMO 复合物中不同细菌叶绿素亚基的位置和能量弛豫，对于涉及七个位置的系统广泛讨论的相干振荡的重要性对于涉及八个位置的系统来说远不那么明显，这实际上是由于初始位置与系统其余部分之间的弱混合。我们建议，相关的光谱密度可以决定能量传输路径，并可能为人工设备中的能量转移提供一种新方法。
