HOW MELATONIN INTERACTS WITH LIPID BILAYERS - A STUDY BY FLUORESCENCEAND ESR SPECTROSCOPIES

ESR spectra of spin labels placed at the membrane surface and at diffe rent depths of the bilayer core, and melatonin fluorescence in the pre sence of lipid vesicles, suggest an average shallow position for the h ormone in the membrane, However, according to the melatonin ability to cross lipid bilayers, nitroxides placed deep in the bilayer were able to quench the melatonin fluorescence, Melatonin membrane partition co efficients were calculated for bilayers in different packing states, a nd similar and rather high values were found, The data presented here may be quite important to the understanding of melatonin physiological actions at the membrane level. (C) 1997 Federation of European Bioche mical Societies.