Reconstitution of the LH1 antenna complex from Rhodospirillum rubrum G9 and wild type
by the use of five carotenoids having different conjugation lengths

Abstract

Five different kinds of carotenoid were reconstituted into the LH1 complexes from Rhodospirillum rubrum G9 and S1; they include neurosporene (the number of conjugated double bonds; n = 9), spheroidene (n = 10), lycopene (n = 11), anhydrorhodovibrin (n = 12) and spirilloxanthin (n = 13). Subpicosecond time-resolved absorption spectra were recorded, and analyzed by means of SVD followed by global fitting in visible region. Further, we tried analysis of energy transfer by the use of the breaching of the Q_y absorption in the near-infrared region.
When n becomes larger, Car-to-BChl energy transfer became slower, but singlet-triplet conversion became faster. Especially, when n increase from 10 to 11, the rate constants change drastically, and energy transfer channels from the 1B_u^- and 2A_g^- state were almost closed. The efficiencies of singlet-energy transfer through the three (1B_u⁺, 1B_u^- and 2A_g^-) channels closely correlated to those of the LH2 complexes.