Fujita Takatoshi, Huh Joonsuk, Saikin Semion K, Brookes Jennifer C, Aspuru-Guzik Alán
Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, 02138, USA,
Photosynth Res. 2014 Jun;120(3):273-89. doi: 10.1007/s11120-014-9978-7. Epub 2014 Feb 7.
We present a theoretical study of excitation dynamics in the chlorosome antenna complex of green photosynthetic bacteria based on a recently proposed model for the molecular assembly. Our model for the excitation energy transfer (EET) throughout the antenna combines a stochastic time propagation of the excitonic wave function with molecular dynamics simulations of the supramolecular structure and electronic structure calculations of the excited states. We characterized the optical properties of the chlorosome with absorption, circular dichroism and fluorescence polarization anisotropy decay spectra. The simulation results for the excitation dynamics reveal a detailed picture of the EET in the chlorosome. Coherent energy transfer is significant only for the first 50 fs after the initial excitation, and the wavelike motion of the exciton is completely damped at 100 fs. Characteristic time constants of incoherent energy transfer, subsequently, vary from 1 ps to several tens of ps. We assign the time scales of the EET to specific physical processes by comparing our results with the data obtained from time-resolved spectroscopy experiments.
基于最近提出的分子组装模型，我们对绿色光合细菌的叶绿体天线复合体中的激发动力学进行了理论研究。我们用于整个天线中激发能量转移（EET）的模型，将激子波函数的随机时间传播与超分子结构的分子动力学模拟以及激发态的电子结构计算相结合。我们通过吸收光谱、圆二色光谱和荧光偏振各向异性衰减光谱表征了叶绿体的光学性质。激发动力学的模拟结果揭示了叶绿体中EET的详细情况。相干能量转移仅在初始激发后的前50飞秒内显著，激子的波状运动在100飞秒时完全衰减。随后，非相干能量转移的特征时间常数从1皮秒到几十皮秒不等。通过将我们的结果与时间分辨光谱实验获得的数据进行比较，我们将EET的时间尺度归因于特定的物理过程。
