ULTRAFAST ENERGY-TRANSFER IN CHLOROSOMES FROM THE GREEN PHOTOSYNTHETIC BACTERIUM CHLOROFLEXUS-AURANTIACUS

Energy transfers between the bacteriochlorophyll c and a antennae in l ight-harvesting chlorosomes from the green bacterium Chloroflexus aura ntiacus have been studied in two-color pump-probe experiments with imp roved sensitivity and wavelength versatility. The BChl c --> BChl a en ergy transfers are well simulated with biexponential kinetics, with li fetimes of 2-3 and 11 ps. They do not exhibit an appreciable subpicose cond component. In the context of a kinetic model for chlorosomes, the se lifetimes suggest that both internal BChl c processes and the BChl c --> BChl a energy-transfer step contribute materially to the empiric al rod-to-baseplate energy-transfer kinetics.