title: Transient absorption study of two-photon excitation mechanism in the LH2 complex from purple bacterium Rhodobacter sphaeroides.
abstract: The mechanism of two-photon excitation of a peripheral light-harvesting complex LH2 (B800-850) from purple bacterium Rhodobacter sphaeroides was explained on the basis of femtosecond transient absorption data. Fast bleaching of the B850 absorption band was measured under two-photon excitation by 1350 nm femtosecond pulses, showing fast subpicosecond arrival of excitation energy to B850 circular aggregates. Any spectral changes connected with the B800 absorption band of B800-BChl molecules were absent. A similar picture was observed under one-photon excitation of the LH2 complex by 675 nm femtosecond pulses. We believe these effects may be attributed to direct excitation of high-energy excitonic states of a B850 circular aggregate or its vibrational manifold in accordance with the model of Abe [Chem. Phys. 2001, 264, 355-363].
authors.affiliation: A. N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Leninskie Gory, 119992 Moscow, Russia.
authors.forename: Ilya
authors.initials: I
authors.lastname: Stepanenko
authors.forename: Viktor
authors.initials: V
authors.lastname: Kompanetz
authors.forename: Zoya
authors.initials: Z
authors.lastname: Makhneva
authors.forename: Sergey
authors.initials: S
authors.lastname: Chekalin
authors.forename: Andrei
authors.initials: A
authors.lastname: Moskalenko
authors.forename: Andrei
authors.initials: A
authors.lastname: Razjivin
mesh_terms: D045342:Light-Harvesting Protein Complexes / Q000378:metabolism*; D017785:Photons; D012242:Rhodobacter sphaeroides / Q000378:metabolism*
chemical_list: D045342:Light-Harvesting Protein Complexes