Issue 42, 2019

The molecular mechanisms of light adaption in light-harvesting complexes of purple bacteria revealed by a multiscale modeling

Abstract

The light-harvesting in photosynthetic purple bacteria can be tuned in response to the light conditions during cell growth. One of the used strategies is to change the energy of the excitons in the major fight-harvesting complex, commonly known as LH2. In the present study we report the first systematic investigation of the microscopic origin of the exciton tuning using three complexes, namely the common (high-light) and the low-light forms of LH2 from Rps. acidophila plus a third complex analogous to the PucD complex from Rps. palustris. The study is based on the combination of classical molecular dynamics of each complex in a lipid membrane and excitonic calculations based on a multiscale quantum mechanics/molecular mechanics approach including a polarizable embedding. From the comparative analysis, it comes out that the mechanisms that govern the adaptation of the complex to different light conditions use the different H-bonding environment around the bacteriochlorophyll pigments to dynamically control both internal and inter-pigment degrees of freedom. While the former have a large effect on the site energies, the latter significantly change the electronic couplings, but only the combination of the two effects can fully reproduce the tuning of the final excitons and explain the observed spectroscopic differences.

Graphical abstract: The molecular mechanisms of light adaption in light-harvesting complexes of purple bacteria revealed by a multiscale modeling

Supplementary files

Article information

Article type
Edge Article
Submitted
13 Jūn. 2019
Accepted
23 Sept. 2019
First published
27 Sept. 2019
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY license

Chem. Sci., 2019,10, 9650-9662

The molecular mechanisms of light adaption in light-harvesting complexes of purple bacteria revealed by a multiscale modeling

F. Cardoso Ramos, M. Nottoli, L. Cupellini and B. Mennucci, Chem. Sci., 2019, 10, 9650 DOI: 10.1039/C9SC02886B

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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