Spectral properties of fluorescent dyes in lecithin vesicles. Probes for the structure of lipid bilayer membranes and for membrane potentials.

Three fluorescent dyes (a merocyanin, a cyanin and a modified umbeliferon) have been incorporated into vesicles from three different lecithins. Their absorption spectrum, emission spectrum and fluorescence polarization in the lipid vesicles has been studied and compared with the spectral properties in homogeneous organic solutions. The reactivity of lipid bound dyes with reagents in the aqueous phase was investigated. The location of various dyes in the lipid membrane and their use as indicators of phase transitions or membrane potentials are discussed.