Effect of Cholesterol and Xanthone on the hydration states of ester and ether lipids by fluorescent probe

HUGO A. PÉREZ; ANTONIO S. ROSAS; JIMENA P. CEJAS; MARÍA DE LOS ANGELES FRIAS

La Plata

Congreso; XLVII Reunión Anual de la Sociedad Argentina de Biofísica; 2018

Sociedad Argentina de Biofísica

Cell membranes influence many cellular functionsand are involved in most cellular communication processes. An importantbiophysical parameter at the molecular level is the ordering degree of the membranedetermining the movement speed of the molecules (lateral diffusion, waterpermeability, etc.) can be modified by cholesterol and structurally analogues compound suchxanthones.However, those properties can also be relatedwith the organization of water molecules in the interphase. The main hydrationcenters in a phosphatidylcholine membrane are the carbonyl and the phosphategroups, in addition to water occluded between the hydrocarbon chains. In this work, the effect of cholesterol andxanthone on the hydration degrees of vesicles (MLV) composed by ester and etherlipids on the same chain length below and above the transition temperature wasstudied using LAURDAN as a fluorescent probe sensitive to polarity. The chemical structures ofthese lipids differ only with respect to the type of bond (carboxylic ester, ether)between the glycerol and the hydrophobic chain attached to the primary hydroxylof glycerol, i.e., ether Pc lacks of a hydration center. The results show that theGPex values are lower for the ether compared to the ester, indicating a higherhydration at the membrane interface in the absence of carbonyl groups, bothbelow and above the transition temperature (Tm). On the other hand, thepresence of cholesterol and xanthone decrease the GPex values in both lipids beingmore noticeable in the ether PC compared to the ester PC. Therefore, weconclude that the absence of carbonyl groups modifies the dipolar relaxation of the immediate environmentof the marker. Therefore, the dehydrating effects of cholesterol could be a consequence ofthe differentability of reorientation of lipid dipoles in the glycerol region and of watermolecules in the other hydration sites. The differences between the effects of xanthone are discussedon structural base.