Optical dephasing in photosynthetic pigment-protein complexes

We have studied optical dephasing in a number of pigment-protein complexes. Remarkably we find that the energies of the modes involved in the dephasing of the optical transition of the 825 nm band of the FMO-complex of Chlorobium tepidum, the blue-shifted B800 band of two mutants of Rhodobacter sphaeroides and the B777 subparticle of the LH1-complex of Rhodospirillum rubrum are the same, 9 and 42 cm(-1). Except for the B777 subparticle, we find that the data can be described using identical coupling strengths for these modes. For the B777 particle the coupling strengths appeared to be slightly larger. The signals from the blue-shifted B800 band of the mutants we ascribe to semi-detached bacteriochlorophyll molecules. These results suggest that bacteriochlorophyll a molecular modes are involved in the dephasing process. (C) 1998 Elsevier Science B.V. All rights reserved.