Effect of Cholesterol and Xanthone in the hydration states of lipid esters and ethers by fluorescent probe

FRIAS, M DE LOS ANGELES; DISALVO ANÍBAL, E.; PEREZ, HUGO ALEJANDRO

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

Sociedad Argentina de Biofisica

Cell membranes influence many cellular functions and are involved in most cellular communication processes1, 2. An important biophysical parameter at the molecular level is the ordering degree of the membrane since it determines the movement speed of the molecules, with a relation inversely proportional to the microviscosity of the membrane. This property is related to water molecules in the interphase3, 4. The main hydration centers are carbonyl and phosphate groups. It has also been reported that water can accumulate between the hydrocarbon chains.In this work Laurdan was used, a fluorescent probe commonly used to sense membrane states and interfacial polarization in cells and in biomimetic systems such as vesicles and monolayers5.The hydration degree of multilamellar vesicles (MLV) composed of ester and ether lipids was studied by LAURDAN in order to determine the influence of each of these centers on the hydration properties of the membrane. In addition, the effect of cholesterol and xanthone on hydration degrees below and above the transition temperature was evaluated. The chemical structures of these lipids differ only with respect to the type of bond (carboxylic ester, ether) between the glycerol and the hydrophobic chain attached to the primary hydroxyl of glycerol.The results showed that the GPex values are lower for the ether compared to the ester, indicating a higher hydration at the membrane interface both below and above the transition temperature (Tm). On the other hand, the presence of cholesterol and xanthone decrease the GPex values in the lipids, producing an ordering at the interface. This effect is more noticeable for the ether compared to the ester. Therefore, we conclude that the spectral differences observed for LAURDAN in ether and ester lipids could be due to different dipolar relaxation of the immediate environment of the marker, that is, reorientation of lipid dipoles in the glycerol region and of water molecules residing in the same