Energy transfer in purple bacterial photosynthetic units from cells grown in various light intensities

Niedzwiedzki, D. M., Gardiner, A. T., Blankenship, R. E. and Cogdell, R. J. (2018) Energy transfer in purple bacterial photosynthetic units from cells grown in various light intensities. Photosynthesis Research, 137(3), pp. 389-402. (doi: 10.1007/s11120-018-0512-1) (PMID:29725994)

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Three photosynthetic membranes, called intra-cytoplasmic membranes (ICMs), from wild-type and the ∆pucBA mutant of the purple phototrophic bacterium Rps. palustris were investigated using optical spectroscopy. The ICMs contain identical light-harvesting complex 1-reaction centers (LH1-RC) but have various spectral forms of light-harvesting complex 2 (LH2). Spectroscopic studies involving steady-state absorption, fluorescence, and femtosecond time-resolved absorption at room temperature and at 77 K focused on inter-protein excitation energy transfer. The studies investigated how energy transfer is affected by altered spectral features of the LH2 complexes as those develop under growth at different light conditions. The study shows that LH1 → LH2 excitation energy transfer is strongly affected if the LH2 complex alters its spectroscopic signature. The LH1 → LH2 excitation energy transfer rate modeled with the Förster mechanism and kinetic simulations of transient absorption of the ICMs demonstrated that the transfer rate will be 2-3 times larger for ICMs accumulating LH2 complexes with the classical B800-850 spectral signature (grown in high light) compared to the ICMs from the same strain grown in low light. For the ICMs from the ∆pucBA mutant, in which the B850 band of the LH2 complex is blue-shifted and almost degenerate with the B800 band, the LH1 → LH2 excitation energy transfer was not observed nor predicted by calculations.

Item Type:Articles
Additional Information:This work was supported by the Photosynthetic Antenna Research Center, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC 0001035.
Keywords:Energy transfer, intra-cytoplasmic membrane, light-harvesting complex, purple bacteria, transient absorption.
Glasgow Author(s) Enlighten ID:Cogdell, Professor Richard and Gardiner, Dr Alastair
Authors: Niedzwiedzki, D. M., Gardiner, A. T., Blankenship, R. E., and Cogdell, R. J.
College/School:College of Medical Veterinary and Life Sciences > Institute of Molecular Cell and Systems Biology
Journal Name:Photosynthesis Research
ISSN (Online):1573-5079
Published Online:03 May 2018
Copyright Holders:Copyright © 2018 Springer Science + Business Media B.V., part of Springer Nature
First Published:First published in Photosynthesis Research 137(3): 389-402
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher

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