FTIR analysis of the gradual hydration on phospholipids systems with and without carbonyl groups

DÍAZ, S. B., GÓMEZ-ZAVAGLIA, A., FAUSTO, R., E., DISALVO, E. A.

Buenos Aires

Congreso; International Workshop on Infrared Spectroscopy Applied to Biological and Biomimetic Systems: From the Isolated Molecule to the Cell; 2007

Facultad de Farmacia y Bioquímica. Cátedra de química General e Inorgánica

The biological systems are limited by membranes which main structure, the lipid bilayer, is stabilized by hydration of phospholipids. Consequently, each process that involve changes in the content of water affects the stability and the properties of the membrane being able to produce serious damages in the cell and its death.  The phospholipids, fundamental molecules of the biological membranes, consist of a phosphatidylcholine or a phosphatidylethanolamine esterificated to a diacylglycerolipids. It has been reported that the carbonyl ester linking the glycerol backbone with the fatty acid chains and the phosphate groups in the polar head are the main hydration sites of fully hydrated phosphatidylcholines (1). The presence of the phosphate groups in such molecules has been related to diverse properties of membrane. Among them, it can be mentioned that the phosphate is the place of hydration of the membranes in which they condense the first six molecules of the eigtheen or twenty that can hydrate the phosphatidylcholines (2,3,4).  FTIR has been shown to be extremely sensitive to show changes on the carbonyl and phosphate groups states of hydration(5). A study of the gradual hydration of phospholipid assemblies by Fourier transform infrared (FTIR) spectroscopy was made (6). The lipid samples were prepared as films probably consisting of aligned multilamellar bilayers of DMPC, etherPC, DMPC/Trehalose and etherPC/trehalose. In addition, frequency shifts in the PO2- and C=O groups were observed by heating the same samples in the solid state. The IR-spectroscopic data were focused in determining the amounts of water incorporated by each phospholipid system as well as the hydration-induced response observed for some absorption bands of the different lipids. This systems showed significant variation in the wavenumber shifts for the PO2- and C=O stretching-vibration modes, obtained as a function of hydration.