Temperature dependent LH1 → RC energy transfer in purple bacteria Tch. tepidum with shiftable LH1-Qy band: A natural system to investigate thermally activated energy transfer in photosynthesis

Fei Ma, Long Jiang Yu, Zheng Yu Wang-Otomo, Rienk Van Grondelle

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    14 Citations (Scopus)

    Abstract

    The native LH1-RC complex of the purple bacterium Thermochromatium (Tch.) tepidum has an ultra-red LH1-Qy absorption at 915 nm, which can shift to 893 and 882 nm by means of chemical modifications. These unique complexes are a good natural system to investigate the thermally activated energy transfer process, with the donor energies different while the other factors (such as the acceptor energy, special pair at 890 nm, and the distance/relative orientation between the donor and acceptor) remain the same. The native B915-RC, B893-RC and B882-RC complexes, as well as the LH1-RC complex of Rhodobacter (Rba.) sphaeroides were studied by temperature-dependent time-resolved absorption spectroscopy. The energy transfer time constants, kET- 1, are 65, 45, 46 and 45 ps at room temperature while 225, 58, 85, 33 ps at 77 K for the B915-RC, B893-RC, B882-RC and Rba. sphaeroides LH1-RC, respectively. The dependences of kET on temperature have different trends. The reorganization energies are determined to be 70, 290, 200 and 45 cm- 1, respectively, by fitting kET vs temperature using Marcus equation. The activation energies are 200, 60, 115 and 20 cm- 1, respectively. The influences of the structure (the arrangement of the 32 BChl a molecules) on kET are discussed based on these results, to reveal how the B915-RC complex accomplishes its energy transfer function with a large uphill energy of 290 cm- 1.

    Original languageEnglish
    Pages (from-to)408-414
    Number of pages7
    JournalBiochimica et Biophysica Acta - Bioenergetics
    Volume1857
    Issue number4
    DOIs
    Publication statusPublished - Apr 1 2016

    Keywords

    • LH1 → RC energy transfer
    • Thermally activated energy transfer
    • Thermochromatium (Tch.) tepidum
    • Time-resolved absorption spectroscopy

    ASJC Scopus subject areas

    • Biophysics
    • Biochemistry
    • Cell Biology

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