Excitonic energy transfer in light-harvesting complexes in purple bacteria
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 lightharvesting systems in purple bacteria. It is found that incl...
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| Main Authors: | , , , , , |
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| Other Authors: | |
| Format: | Article |
| Language: | English |
| Published: |
2012
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| Online Access: | https://hdl.handle.net/10356/94749 http://hdl.handle.net/10220/8289 |
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| Institution: | Nanyang Technological University |
| Language: | English |
| Summary: | 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 lightharvesting
systems in purple bacteria. It is found that inclusion of long-range dipolar interactions
in the two methods results in significant increases 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
interesting role of dipolar interaction in increasing energy transfer efficiency by introducing multiple
intra/inter-ring transfer paths. Importantly, the time scale ( 4ps) 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 interaction can induce symmetry breaking which leads to global
minima and local minima of the average trapping time when there is a finite value of non-zero
dephasing rate, suggesting that environment plays a role in preserving quantum coherent energy
transfer. In contrast, dephasing comes into play only when the perfect cylindrical symmetry in
the hypothetic system is broken. This study has revealed that dipolar interaction between chromophores
may play an important part in the high energy transfer efficiency in the LH2 system and
many other natural photosynthetic systems. |
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