Lack of Excitation Energy Transfer from the Bacteriochlorophyll Soret Band to Carotenoids in Photosynthetic Complexes of Purple Bacteria
Language English Country United States Media print-electronic
Document type Journal Article, Research Support, Non-U.S. Gov't
- MeSH
- Bacteriochlorophylls MeSH
- Chromatiaceae MeSH
- Ectothiorhodospira MeSH
- Spectrometry, Fluorescence MeSH
- Photosynthetic Reaction Center Complex Proteins * metabolism MeSH
- Carotenoids MeSH
- Energy Transfer MeSH
- Proteobacteria metabolism MeSH
- Rhodobacter sphaeroides * metabolism MeSH
- Light-Harvesting Protein Complexes metabolism MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Names of Substances
- Bacteriochlorophylls MeSH
- Photosynthetic Reaction Center Complex Proteins * MeSH
- Carotenoids MeSH
- Light-Harvesting Protein Complexes MeSH
The excitation energy transfer (EET) from the bacteriochlorophyll (BChl) Soret band to the second excited state(s) (S2) of carotenoids in pigment-protein complexes of purple bacteria was investigated. The efficiency of EET was determined, based on fluorescence excitation and absorption spectra of chromatophores, peripheral light-harvesting complexes (LH2), core complexes (LH1-RC), and pigments in solution. Carotenoid-containing and carotenoid-less samples were compared: LH1-RC and LH2 from Allochromatium minutissimum, Ectothiorhodospira haloalkaliphila, and chromatophores from Rhodobacter sphaeroides and Rhodospirillum rubrum wild type and carotenoid-free strains R-26 and G9. BChl-to-carotenoid EET was absent, or its efficiency was less than the accuracy of the measurements of ∼5%. Quantum chemical calculations support the experimental results: The transition dipole moments of spatially close carotenoid/BChl pairs were found to be nearly orthogonal. The structural arrangements suggest that Soret EET may be lacking for the studied systems, however, EET from carotenoids to Qx appears to be possible.
Faculty of Biology Lomonosov Moscow State University 119991 Moscow Russia
Institute of Chemistry and Biochemistry Freie Universität Berlin 14195 Berlin Germany
References provided by Crossref.org
Carotenoid responds to excess energy dissipation in the LH2 complex from Rhodoblastus acidophilus
