[Excitation energy transfer between chlorophyll a molecules in detergent solutions]

Chlorophyll-a absorption and luminescence as well as the transfer of electronic excitation energy between chlorophyll-a molecules were studied in micellar solutions of triton X-100 as a function of both chlorophyll-a and detergent concentrations. It is shown that the spectral properties of chlorophyll-a are closely related to the ratio between the concentrations of X-100 and chlorophyll-a. Concurrent evaluation of the curves for depolarization and relative quantum yield of fluorescence show that two different mechanisms of energy transfer are involved: energy transfer between monomers of chlorophyll-a, and energy transfer from excited monomers to aggregates of chlorophyll-a. Using the theoretical value for the critical distance of energy transfer (Ro=56-58 A) as well as experimental data from depolarization and fluorescence curves for solutions containing 3-10-3 M triton X-100 we determined the local concentration of chlorophyll-a in the detergent micelles.