Excited States and Charge Separation in Membranes of the Green Sulfur Bacterium Prosthecochloris aestuarii

Abstract

AbstractTime‐resolved absorbance changes were measured in isolated membranes, depleted of chlorosomes, and in the Fenna‐Matthews‐Olson (FMO) complex of the green sulfur bacterium Prosthecochloris aestuarri. The isolated FMO complex showed a biphasic decay of excited bacteriochlorophyll a (BChl a) with time constants of about 80 and 1400 ps. Approximately the same time constants were observed upon excitation of isolated membranes together with a component of about 30 ps. It is concluded that the efficiency of energy transfer from the FMO to the core complex is very low, in agreement with earlier measurements of the efficiency of charge separation. The 30 ps decay component is ascribed to trapping of the excitation energy from the core BChl a by the reaction center.