Interphase Properties of Lipid Membranes II: Does FTIR allow to differentiate hydration sites in phospholipids?

JIMENA CEJAS; MARIA DE LOS ANGELES FRIAS; ROSA, SEBASTIAN; DISALVO ANÍBAL, E.; PEREZ, HUGO ALEJANDRO

San Luis

Encuentro; VIII Encuentro de Física y Química de Superficies; 2018

The physical state of water in lipid membranes has a determinant role in the physiological reactions1. Water sorption characteristics are reflective of the chemical and structural composition of lipid membranes and the temperature at which hydration takes place. Changes in the sorption characteristics with temperature and hydration level suggest that water induces structural changes that can be confirmed and correlated with molecular vibration frequencies by FTIR-ATR techniques2. The main purpose of this work is to demonstrate that FTIR is a suitable technique to study and differentiate the structural changes that take place during water sorption in a lipid membrane. Water sorption in lipids can take place at different sites characterized by different affinities: strong binding related to Phosphate and Carbonyl groups, weak ones related to confined water between acyl chains3, and water binding to already adsorbed water molecules. D´Arcy/Watt mathematical model4 was developed to describe sorption on a wide range of systems considering different energies of sorption sites and it?s a convenient model to describe water sorption in membranes. Dipalmitoyl phosphatidylcholine liposomes (DPPC) were selected to apply D´Arcy/Watt model. DPPC membranes present saturated bonds and the two main strong hydration sites: phosphate and carbonyl groups. It is also important to consider acyl chains as a new center of hydration. The relevance of this data in relation to the dynamic properties of lipid bilayers are discussed in correlation to fluorescence and monolayers results (See poster I and III).