The role of charge-transfer states in the spectral tuning of antenna complexes of purple bacteria

Nottoli, M., Jurinovich, S., Cupellini, L., Gardiner, A. T., Cogdell, R. and Mennucci, B. (2018) The role of charge-transfer states in the spectral tuning of antenna complexes of purple bacteria. Photosynthesis Research, 137(2), pp. 215-226. (doi:10.1007/s11120-018-0492-1) (PMID:29502240)

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Abstract

The LH2 antenna complexes of purple bacteria occur, depending on light conditions, in various different spectroscopic forms, with a similar structure but different absorption spectra. The differences are related to point changes in the primary amino acid sequence, but the molecular-level relationship between these changes and the resulting spectrum is still not well understood. We undertook a systematic quantum chemical analysis of all the main factors that contribute to the exciton structure, looking at how the environment modulates site energies and couplings in the B800-850 and B800-820 spectroscopic forms of LH2. A multiscale approach combining quantum chemistry and an atomistic classical embedding has been used where mutual polarization effects between the two parts are taken into account. We find that the loss of hydrogen bonds following amino acid changes can only explain a part of the observed blue-shift in the B850 band. The coupling of excitonic states to charge-transfer states, which is different in the two forms, contributes with a similar amount to the overall blue-shift.

Item Type:Articles
Additional Information:ATG and RJC gratefully acknowledge funding from the Photosynthetic Antenna Research Center, an Energy Frontier Research Center funded by the DOE, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC 0001035.
Keywords:Antenna complex, Excitonic model, Quantum chemistry
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Cogdell, Professor Richard and Gardiner, Dr Alastair
Authors: Nottoli, M., Jurinovich, S., Cupellini, L., Gardiner, A. T., Cogdell, R., and Mennucci, B.
College/School:College of Medical Veterinary and Life Sciences > Institute of Molecular Cell and Systems Biology
Journal Name:Photosynthesis Research
Publisher:Springer
ISSN:0166-8595
ISSN (Online):1573-5079
Published Online:03 March 2018
Copyright Holders:Copyright © 2018 Springer Science + Business Media B.V., part of Springer Nature
First Published:First published in Photosynthesis Research 137(2): 215-226
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher

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