BEHAVIOR OF HETEROEXCIMER SYSTEMS IN SINGLE BILAYER LIPOSOMES

Abstract— Behavior of heteroexcimers formed between pyrene moieties incorporated at varying depths from the charged surface of vesicles and exogeneous N, N-dimethylaniline during the lifetime of excited pyrene moiety have been investigated by means of fluorescence measurements and laser photolysis. Fluorescence studies show that the fluorescence quenching kinetics in liposomes is rather similar to that in homogeneous bulk solutions, in contrast to the case of ordinary micellar solutions. Weak heteroexcimer fluorescence as well as transient absorption bands of ion radicals produced as a consequence of electron transfer from the amine to the excited pyrenyl group were observed. Comparison of the present results with those in homogeneous solutions indicates that the polar environment where dielectric constant is as large as 10 is attained in the hydrocarbon core of the liposomes. The polar environment of the fatty acid chains suggests the presence of water molecules penetrated into the hydrocarbon core.