Ab initio description of the quantum mechanics in light-harvesting complexes of purple bacteria

结合高分辨率晶体结构、超快光谱和量子化学计算，研究了光合系统结构与功能（即光收集）之间复杂而微妙的关系。该方案的目的是从紫色细菌嗜酸红假单胞菌的光收集系统2 （LH2）的可用晶体结构开始，进行分子动力学模拟，然后将获得的核位置的热波动作为量子化学计算的输入。在这些量子化学计算结果的基础上，应应用一个改进的量子力学模型来确定光谱。这样就可以建立一个前所未有的精度模型，而不需要拟合参数。除了LH2环系综的静态和瞬态光谱外，还需要关注单分子光谱的理论确定和分类。该模型还允许将类胡萝卜素纳入模型，并将它们视为与构成环系统的细菌叶绿素相同的基础。最近对类胡萝卜素和LH2环之间能量转移的相干控制实验建模是该项目的进一步目标。

The complex and subtle relationship between structure and function, i.e. light-harvesting, of photosynthetic systems has been studied conjointly with high-resolution crystallographic structures, ultrafast spectroscopy and quantum chemical calculations. The aim of the proposal is to start at the available crystal structure of the light-harvesting system 2 (LH2) of purple bacterium Rhodopseudomonas acidophila, perform a molecular dynamics simulation and then use the obtained thermal fluctuations of the nuclear positions as input for quantum chemical calculations. Based on the results of these quantum chemical calculations a refined quantum mechanical model shall be applied to the determination of optical spectra. This way one can construct a model with unprecedented accuracy and without fitting parameters. Besides static and transient spectra of ensembles of LH2 rings, another focus shall be on the theoretical determination and classification of single-molecule spectra. The model also allows for the incorporation of the carotenoids into the model and to treat them on the same footing as the bacteriochlorophylls which constitute the ring systems. Modeling of recent coherent control experiments on the energy transfer between carotenoids and the rings in the LH2 is a further goal of the project.