Effect of cholesterol concentration on the fluorescence ratio, R, and the dipole potential, ψd, of DMPC (▪), egg PC (•), and DOPC (▴) vesicles. [di-8-ANEPPS] = 5 μM, [PC] = 3.6 mM. For DMPC, the measurements were performed at 30°C. For DOPC and egg PC, the measurements were performed at room temperature.