Baker, Lewis A. and Habershon, Scott (2015) Robustness, efficiency, and optimality in the Fenna-Matthews-Olson photosynthetic pigment-protein complex. The Journal of Chemical Physics, 143 (10). 105101. doi:10.1063/1.4930110 ISSN 0021-9606.

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Abstract

Pigment-protein complexes (PPCs) play a central role in facilitating excitation energy transfer (EET) from light-harvesting antenna complexes to reaction centres in photosynthetic systems; understanding molecular organisation in these biological networks is key to developing better artificial light-harvesting systems. In this article, we combine quantum-mechanical simulations and a network-based picture of transport to investigate how chromophore organization and protein environment in PPCs impacts on EET efficiency and robustness. In a prototypical PPC model, the Fenna-Matthews-Olson (FMO) complex, we consider the impact on EET efficiency of both disrupting the chromophore network and changing the influence of (local and global) environmental dephasing. Surprisingly, we find a large degree of resilience to changes in both chromophore network and protein environmental dephasing, the extent of which is greater than previously observed; for example, FMO maintains EET when 50% of the constituent chromophores are removed, or when environmental dephasing fluctuations vary over two orders-of-magnitude relative to the in vivo system. We also highlight the fact that the influence of local dephasing can be strongly dependent on the characteristics of the EET network and the initial excitation; for example, initial excitations resulting in rapid coherent decay are generally insensitive to the environment, whereas the incoherent population decay observed following excitation at weakly coupled chromophores demonstrates a more pronounced dependence on dephasing rate as a result of the greater possibility of local exciton trapping. Finally, we show that the FMO electronic Hamiltonian is not particularly optimised for EET; instead, it is just one of many possible chromophore organisations which demonstrate a good level of EET transport efficiency following excitation at different chromophores. Overall, these robustness and efficiency characteristics are attributed to the highly connected nature of the chromophore network and the presence of multiple EET pathways, features which might easily be built into artificial photosynthetic systems.

Item Type:	Journal Article
Subjects:	Q Science > QP Physiology
Divisions:	Faculty of Science, Engineering and Medicine > Science > Chemistry
Library of Congress Subject Headings (LCSH):	Photosynthesis, Photosynthetic pigments
Journal or Publication Title:	The Journal of Chemical Physics
Publisher:	American Institute of Physics
ISSN:	0021-9606
Official Date:	9 September 2015
Dates:	Date Event 9 September 2015 Published 21 August 2015 Accepted 9 April 2015 Submitted
Volume:	143
Number:	10
Article Number:	105101
DOI:	10.1063/1.4930110
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access
Date of first compliant deposit:	26 October 2016
Date of first compliant Open Access:	26 October 2016
Funder:	Engineering and Physical Sciences Research Council (EPSRC)
Grant number:	EP/F500378/1

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