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 ab out 20% to the total absorption of the integral B800-850 antenna. In the la tter 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 approximate to 10(13) s(-1)). (C) 1999 Elsevier Science B.V. All rights reserved.