Kundu Sohang, Dani Reshmi, Makri Nancy
Department of Chemistry, University of Illinois, Urbana, IL 61801, USA.
Department of Physics, University of Illinois, Urbana, IL 61801, USA.
Sci Adv. 2022 Oct 28;8(43):eadd0023. doi: 10.1126/sciadv.add0023. Epub 2022 Oct 26.
The efficient, directional transfer of absorbed solar energy between photosynthetic light-harvesting complexes continues to pose intriguing questions. In this work, we identify the pathways of energy flow between the B800 and B850 rings in the LH2 complex of using fully quantum mechanical path integral methods to simulate the excited-state dynamics of the 24 bacteriochlorophyll molecules and their coupling to 50 normal mode vibrations in each chromophore. While all pigments are identical, the tighter packing of the inner B850 ring is responsible for the thermodynamic stabilization of the inner ring. Molecular vibrations enable the 1-ps flow of energy to the B850 states, which would otherwise be kinetically inaccessible. A classical treatment of the vibrations leads to uniform equilibrium distribution of the excitation, with only 67% transferred to the inner ring. However, spontaneous fluctuations associated with the quantum motion of the nuclei increase the transfer efficiency to 90%.
光合光捕获复合物之间吸收太阳能的高效、定向转移仍然存在一些有趣的问题。在这项工作中,我们使用完全量子力学路径积分方法来模拟24个细菌叶绿素分子的激发态动力学及其与每个发色团中50个简正模式振动的耦合,从而确定了LH2复合物中B800和B850环之间的能量流动途径。虽然所有色素都是相同的,但内部B850环更紧密的堆积导致了内环的热力学稳定。分子振动使得能量能够在1皮秒内流向B850态,否则在动力学上是无法实现的。对振动的经典处理导致激发的均匀平衡分布,只有67%转移到内环。然而,与原子核量子运动相关的自发涨落将转移效率提高到了90%。