Fluorescence stopped-flow study of the interaction of alkylpyridinium salts and pyrene-substituted fatty acids with lecithin vesicles

The migration of alkylpyridinium surfactants and pyrene-substituted fatty acids between vesicles has been studied. The results are in accord with the assumption of diffusion-controlled processes. Changes in relaxation time with charge type, degree of ionization, pH, and alkyl chain length of the migrating species are investigated and discussed.The presence of a slower relaxation type, apparently due to a transmembrane transport was established in the case of the pyridinium surfactants, but could not be found for pyrene-substituted fatty acids. Fluorescence-quenching studies indicate that these are present at both vesicle interfaces.