Photophysical characterization of the B800-depleted light harvesting complex B850 of Rhodobacter sphaeroides: Implications to the ultrafast energy transfer 800→850 nm

From the isolated LH2 antenna of Rhodobacter sphaeroides, called B800-850, the bacteriochlorophyll a pigment complement BChl-B800, mainly responsible for the 800 nm absorption band, has been extracted. The remaining complex, with the main NIR absorption peaking at 850 nm (termed pure (p) B850), has a small but distinct sideband in the 800 nm region and contributes there about 20% to the total absorption of the integral B800-850 antenna. In the latter the energy transfer 800→850 nm is per se (at least) biphasic with the pB850 intra-aggregate relaxation as the fastest component known so far (k≈1013 s−1).