title: Singlet-triplet fission of carotenoid excitation in light-harvesting LH2 complexes of purple phototrophic bacteria.
abstract: The current generally accepted structure of light-harvesting LH2 complexes from purple phototrophic bacteria conflicts with the observation of singlet-triplet carotenoid excitation fission in these complexes. In LH2 complexes from the purple bacterium Allochromatium minutissimum, a drop in the efficiency of carotenoid triplet generation is demonstrated, which correlates with the extent of selective photooxidation of bacteriochlorophylls absorbing at ~850 nm. We conclude that singlet-triplet fission of carotenoid excitation proceeds with participation of these excitonically coupled bacteriochlorophylls. In the framework of the proposed mechanism, the contradiction between LH2 structure and photophysical properties of carotenoids is eliminated. The possibility of singlet-triplet excitation fission involving a third mediator molecule was not considered earlier.
authors.affiliation: Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia. ikleonik@yandex.ru.
authors.forename: I B
authors.initials: IB
authors.lastname: Klenina
authors.forename: Z K
authors.initials: ZK
authors.lastname: Makhneva
authors.forename: A A
authors.initials: AA
authors.lastname: Moskalenko
authors.forename: N D
authors.initials: ND
authors.lastname: Gudkov
authors.forename: M A
authors.initials: MA
authors.lastname: Bolshakov
authors.forename: E A
authors.initials: EA
authors.lastname: Pavlova
authors.forename: I I
authors.initials: II
authors.lastname: Proskuryakov
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D001429:Bacteriochlorophylls / Q000737:chemistry; D002338:Carotenoids / Q000737:chemistry*; D002841:Chromatiaceae / Q000378:metabolism*; D007700:Kinetics; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry* / Q000378:metabolism; D010084:Oxidation-Reduction; D011789:Quantum Theory
chemical_list: D001426:Bacterial Proteins; D001429:Bacteriochlorophylls; D045342:Light-Harvesting Protein Complexes; D002338:Carotenoids