Ultrafast energy transfer in chlorosomes from the green photosynthetic bacterium Chloroflexus aurantiacus.

Energy transfers between the bacteriochlorophyll c and a antennae in light-harvesting chlorosomes from the green bacterium Chloroflexes aurantiacus have been studied in two-color pump-probe experiments with improved sensitivity and wavelength versatility. The BChl c --> BChl a energy transfers are well simulated with biexponential kinetics, with lifetimes of 2-3 and 11 ps. They do not exhibit an appreciable subpicosecond component. In the context of a kinetic model for chlorosomes, these lifetimes suggest that both internal BChl c processes and the BChl c --> BChl a energy-transfer step contribute materially to the empirical rod-to-baseplate energy-transfer kinetics.