Effects of Cholesterol Concentrations on Egg-phosphatidylcholine - Dihexadecyl-phosphate Liposomes Studied by CW ESR and FT - ESEEM Spectroscopy

摘要

The influence of cholesterol on water penetration depth as well as on the motional properties of spin-labelled stearic acids (n-SASL. n = 5, 7, 10, 12, 16) in liposomes composed of egg-yolk phosphatidylcholine (egg-PC) and dihexadecyl-phosphate (DHP) was studied by electron spin echo envelope modulation (ESEEM) and continuous wave electron spin resonance (CW ESR) spectroscopy. An increased amount of D(2)O molecules in the neighbourhood of the nitroxide moiety bound at 5- and 7-SASL, concomitant with an absence of D(2)O at 10-SASL and 16-SASL was determined in the presence of cholesterol in x = 8, 15, 29 38, and 45 % (mole fraction). At 16-SASL, presence of cholesterol at any of the concentrations examined caused increased amplitude of the librational motion of the nitroxide moiety as compared to that amplitude in the absence of cholesterol, These results indicate that the inclusion of cholesterol increases water penetration in the polar region of the bilayer and influences structural change in the hydrophobic core of membrane.