ENERGY-TRANSFER BETWEEN ANTENNA COMPLEXES IN THE PURPLE SULFUR BACTERIA CHROMATIUM-TEPIDUM AND CHROMATIUM-VINOSUM

Energy transfer between antenna complexes was studied by means of time resolved absorption spectroscopy in the purple sulfur bacteria Chroma tium tepidum and C. vinosum. The first species contains only one perip heral antenna complex, B800-850, the other one has two, B800-850 and B 800-820. Results obtained with chromatophores of C. tepidum indicated two Lime constants for energy transfer from B800-850 to the core compl ex, of 10 ps and a smaller one of 30 ps, suggesting non-uniform distan ces between the peripheral and core complexes. Similar results were ob tained with C. vinosum, where time constants of 7 and 30 ps were found . Energy transfer from B800-820 to B800-850 was significantly faster. These results show that the rates of energy transfer from bacteriochlo rophyll 850 to the core complex in the purple sulfur bacteria studied are quite similar to those found in purple non-sulfur bacteria. This m ay seem remarkable in view of the fact that the core antenna in C. tep idum absorbs at the unusually long wavelength of 918 nm, but a calcula tion indicates that the overlap integral for energy transfer to the co re is not dramatically less than in C. vinosum.