Hydration of Carbonyls and Phosphate in Lipid Bilayers and Its Effects on Dipole Potential, Polarity and Packing

DISALVO E. A.; LAIRION F.; BERNIK D.,; ZUBIRI D.,; TYMCZYSZYN E.,; DIAZ S.

Caxambú-Brasil

Workshop; XXX Reunión Anual de la Sociedad Brasilera de Bioquímica y Biología Molecular; 2001

Water in a lipid membrane is mostly organized around the polar head groups of the phospholipids molecules. This hydration layer is one of the major contributions to the dipole potential of the membrane. However, it is not known which are the main hydration sites in which water is polarised  and how many water molecules are involved around carbonyls, phosphates and choline groups. In addition, it would be of interest to know how the partial elimination of water from these sites affects the interfacial properties. In work the shift in the frequency of carbonyls and phosphate groups in the presence of molecules that may displace water such as trehalose and phloretin has been measured by Fourier Transform Infrared Spectroscopy. It was found that the water firmly bound to carbonyls and phosphate contributes to the dipole potential on the membrane. The binding of trehalose and phloretin to the carbonyl and phosphate groups affects the packing and the polarity on the glycerol backbone. Measured by using fluorescent probes inserted at different levels of the bilayers interface. It is concluded that the displacement of defined amount of water molecules from each of those groups affects the electrical profile of the lipid interface. These results are of importance in the understanding of the mechanism of binding and penetration of peptides and polysaccharides.