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The nature of broad band in the two-photon excitation spectra of light-harvesting complexes from purple bacteriaтезисы доклада
- Авторы: Stepanenko I., Kompanetz V., Makhneva Z., Chekalin S., Moskalenko A., Razjivin A.
- Сборник: Abstracts of the International conference “Photosynthesis Research for Sustainability”
- Тезисы
- Год издания: 2011
- Место издания: Baku, Azerbaijan
- Первая страница: 79
- Последняя страница: 79
- Аннотация: The processes of excitation energy transfer (EET) via pigments of the light-harvesting antenna and their spectral manifestations are still in discussion. For example there is a question about the nature of the broad band near 1300 nm in two-photon excitation (TPE) spectra of light-harvesting complexes from purple bacteria. Earlier the occurrence of this band was taken as an evidence for the participation of “dark” carotenoid S1 state in EET processes (see [Walla et al., Proc. Nat. Acad. Sci. U.S.A. 97, 10808-10813 (2000)] and references in it). However we showed that TPE spectrum of LH2 fluorescence within 1200-1500 nm is not associated with carotenoids [Stepanenko et al., J. Phys. Chem. B. 113(34), 11720–11723 (2009)]. Now we applied femtosecond pump and probe spectroscopy trying to investigate the mechanism of two-photon excitation of a peripheral light-harvesting complex LH2 (B800-850) from purple bacterium Rhodobacter sphaeroides (wild type). The two-photon excitation spectrum featured a wide excitation band around 1350 nm (2 x 675 nm, 14 800 cm-1). Fast bleaching of the B850 absorption band was measured under two-photon excitation by 1350 nm femtosecond pulses, showing fast sub-picosecond arrival of excitation energy to B850 circular aggregates. Any spectral changes connected with the B800 absorption band of B800-BChl molecules were absent. 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 S. Abe [Abe, Chemical Physics 264, 355–363 (2001)].
- Добавил в систему: Разживин Андрей Павлович