Excitonic energy transfer in light-harvesting complexes in purple bacteria
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Cao_Excitonic energy.pdf
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Author(s)
Ye, Jun
Sun, Kewei
Zhao, Yang
Yu, Yunjin
Kong Lee, Chee
Cao, Jianshu
Date Issued
June 2012
Journal
The Journal of Chemical Physics
Publisher
American Institute of Physics (AIP)
Citation
Ye, Jun, Kewei Sun, Yang Zhao, Yunjin Yu, Chee Kong Lee, and Jianshu Cao. “Excitonic energy transfer in light-harvesting complexes in purple bacteria.” The Journal of Chemical Physics 136, no. 24 (2012): 245104. © 2012 American Institute of Physics
Version
Final published version
Abstract
Two distinct approaches, the Frenkel-Dirac time-dependent variation and the Haken-Strobl model, are adopted to study energy transfer dynamics in single-ring and double-ring light-harvesting (LH) systems in purple bacteria. It is found that the inclusion of long-range dipolar interactions in the two methods results in significant increase in intra- or inter-ring exciton transfer efficiency. The dependence of exciton transfer efficiency on trapping positions on single rings of LH2 (B850) and LH1 is similar to that in toy models with nearest-neighbor coupling only. However, owing to the symmetry breaking caused by the dimerization of BChls and dipolar couplings, such dependence has been largely suppressed. In the studies of coupled-ring systems, both methods reveal an interesting role of dipolar interactions in increasing energy transfer efficiency by introducing multiple intra/inter-ring transfer paths. Importantly, the time scale (4 ps) of inter-ring exciton transfer obtained from polaron dynamics is in good agreement with previous studies. In a double-ring LH2 system, non-nearest neighbor interactions can induce symmetry breaking, which leads to global and local minima of the average trapping time in the presence of a non-zero dephasing rate, suggesting that environment dephasing helps preserve quantum coherent energy transfer when the perfect circular symmetry in the hypothetic system is broken. This study reveals that dipolar coupling between chromophores may play an important role in the high energy transfer efficiency in the LH systems of purple bacteria and many other natural photosynthetic systems.
MIT Department
Massachusetts Institute of Technology. Department of Chemistry
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DOI of Published Version
https://doi.org/10.1063/1.4729786
