Energy transfer processes in Rhodopseudomonas palustris grown under low-light conditions. Heterogeneous composition of LH 2 complexes and parallel energy flow pathways.
Excitation energy flow in the purple photosynthetic bacterium Rhodopseudomonas palustris grown under a low-light intensity was studied by time-resolved fluorescence spectroscopy in the ps time range. This bacterium synthesized the B824 component under this light condition. Time-resolved spectra at 20 degrees C indicated the sequential energy flow in the order of B803, B856, B882 and B900, long wavelength antenna. An emission from B803 was not observed. A remarkable feature was the emission from B824 throughout the measuring time. After the excitation pulse of 100 ps, the spectra did not change any further, indicating the establishment of an equilibrium among components. Based on the energy distribution after equilibrium, parallel energy transfer pathways to LH 1 were suggested; one including B824 integrated in the B803-824-856 complex, and the other, from the B803-856 complex to B882. The latter was the dominant energy flow pathway in this bacterium.
Nishimura
Y
Y
Department of Chemical Process Engineering, Faculty of Engineering, Hokkaido University, Sapporo, Japan.
Shimada
K
K
Yamazaki
I
I
Mimuro
M
M
D001426:Bacterial Proteins / Q000378:metabolism*; D004735:Energy Transfer; D008027:Light; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins / Q000378:metabolism*; D045332:Photosystem II Protein Complex; D010860:Pigments, Biological / Q000378:metabolism*; D012241:Rhodopseudomonas / Q000254:growth & development / Q000378:metabolism*; D013050:Spectrometry, Fluorescence
D001426:Bacterial Proteins; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D010860:Pigments, Biological; C023693:protein complex B800-850, Rhodobacter