FEMTOSECOND DYNAMICS OF CAROTENOID-TO-BACTERIOCHLOROPHYLL A ENERGY-TRANSFER IN THE LIGHT-HARVESTING ANTENNA COMPLEXES FROM THE PURPLE BACTERIUM CHROMATIUM-PURPURATUM

Citation
Po. Andersson et al., FEMTOSECOND DYNAMICS OF CAROTENOID-TO-BACTERIOCHLOROPHYLL A ENERGY-TRANSFER IN THE LIGHT-HARVESTING ANTENNA COMPLEXES FROM THE PURPLE BACTERIUM CHROMATIUM-PURPURATUM, Chemical physics, 210(1-2), 1996, pp. 195-217
Citations number
41
Categorie Soggetti
Physics, Atomic, Molecular & Chemical
Journal title
ISSN journal
03010104
Volume
210
Issue
1-2
Year of publication
1996
Pages
195 - 217
Database
ISI
SICI code
0301-0104(1996)210:1-2<195:FDOCAE>2.0.ZU;2-L
Abstract
The energy transfer from the carotenoid okenone to bacteriochlorophyll a (Bchl a) in the light harvesting complex B800-830 and chromatophore s of Chromatium purpuratum was studied by steady-state fluorescence an d femtosecond transient absorption spectroscopy. By comparing the fluo rescence excitation and the absorption spectra of the B800-830 antenna complex the total energy transfer efficiency of the okenone-to-Bchl a transfer was determined to 95 +/- 5%. A fast (< 200 fs) transfer from (at least) one carotenoid was observed to the B830 chlorophylls. This transfer was found by fs anisotropy measurements to be a transfer fro m the okenone S-2 state to the Bchl a Q(x) state, probably caused by t he dipole-dipole (Forster) mechanism. Later the low-lying okenone S-1 state, which has a lifetime of similar to 8 ps in solution, was observ ed transferring energy to the B830 pool in similar to 3.8 ps, while a second carotenoid transferred its energy also from the S, state to B80 0 in similar to 0.5 ps. The results are discussed in relation to the c rystal structure of the B800-850 complex of Rhodopseudomonas acidophil a [McDermott et al. Nature 374 (1995)].