Electron spin echo modulation studies of doxylstearic acid spin probes in frozen dihexadecyl phosphate and dioctadecyldimethylammonium chloride vesicles: interaction of the spin probe with deuterated water and effects of cholesterol addition

Abstract

Electron spin echo studies have been carried out for a series of x-doxylstearic acid (x=5, 7, 10, 12, and 16) and 3-doxyl-5α-cholestane spin probes in frozen deuterated aqueous solutions of anionic dihexadecyl phosphate (DHP) vesicles and cationic dioctadecyldimethylammonium chloride (DODAC) vesicles. Modulation effects due to interactions of the spin probe nitroxide group with D 2 O at the vesicle interface give distance-based information which can be used to draw conclusions about the ordering and chain packing of the vesicles