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

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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

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Publication details

The article was received on 13 Jun 2019, accepted on 23 Sep 2019 and first published on 27 Sep 2019


Article type: Edge Article
DOI: 10.1039/C9SC02886B
Chem. Sci., 2019, Advance Article
  • Open access: Creative Commons BY license
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    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, Advance Article , DOI: 10.1039/C9SC02886B

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