Niedzwiedzki, D.M., Dilbeck, P.L., Tang, Q. et al. (4 more authors) (2016) New insights into the photochemistry of carotenoid spheroidenone in light-harvesting complex 2 from the purple bacterium Rhodobacter sphaeroides. Photosynthesis Research. ISSN 0166-8595
Abstract
Light-harvesting complex 2 (LH2) from the semi-aerobically grown purple phototrophic bacterium Rhodobacter sphaeroides was studied using optical (static and time-resolved) and resonance Raman spectroscopies. This antenna complex comprises bacteriochlorophyll (BChl) a and the carotenoid spheroidenone, a ketolated derivative of spheroidene. The results indicate that the spheroidenone-LH2 complex contains two spectral forms of the carotenoid: (1) a minor, ‘‘blue’’ form with an S2 (11 Bu ?) spectral origin band at 522 nm, shifted from the position in organic media simply by the high polarizability of the binding site, and (2) the major, ‘‘red’’ form with the origin band at 562 nm that is associated with a pool of pigments that more strongly interact with protein residues, most likely via hydrogen bonding. Application of targeted modeling of excited-state decay pathways after carotenoid excitation suggests that the high (92%) carotenoid-to-BChl energy transfer efficiency in this LH2 system, relative to LH2 complexes binding carotenoids with comparable double-bond conjugation lengths, derives mainly from resonance energy transfer from spheroidenone S2 (11 Bu ?) state to BChl a via the Qx state of the latter, accounting for 60% of the total transfer. The elevated S2 (11 Bu ?) ? Qx transfer efficiency is apparently associated with substantially decreased energy gap (increased spectral overlap) between the virtual S2 (11 Bu ?) ? S0 (11 Ag -) carotenoid emission and Qx absorption of BChl a. This reduced energetic gap is the ultimate consequence of strong carotenoid–protein interactions, including the inferred hydrogen bonding
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | The Author(s) 2016. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://crea tivecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. |
Keywords: | Carotenoids; Energy transfer; Ultrafast spectroscopy; Light-harvesting complex; Purple bacteria |
Dates: |
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Institution: | The University of Sheffield |
Academic Units: | The University of Sheffield > Faculty of Science (Sheffield) > School of Biosciences (Sheffield) > Department of Molecular Biology and Biotechnology (Sheffield) |
Funding Information: | Funder Grant number BIOTECHNOLOGY AND BIOLOGICAL SCIENCES RESEARCH COUNCIL (BBSRC) BB/M000265/1 EUROPEAN RESEARCH COUNCIL SYNTHPHOTO - 338895 |
Depositing User: | Symplectic Sheffield |
Date Deposited: | 23 Nov 2016 09:31 |
Last Modified: | 23 Nov 2016 09:31 |
Published Version: | http://doi.org/10.1007/s11120-016-0322-2 |
Status: | Published |
Publisher: | Springer Verlag |
Refereed: | Yes |
Identification Number: | 10.1007/s11120-016-0322-2 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:108095 |