Phase transition of binary lipid mixtures: a combined study by Zeta Potential and DSC

MARIA B. SIERRA; MARCELA A. MORINI; VIVIANA I. PEDRONI; ANIBAL DISALVO

Santiago del Estero

Congreso; SAB2015, XLIV Reunión Anual de la Sociedad Argentina de Biofísica; 2015

We studied the system DMPC/DPPC in aqueous suspensions in the presence or absence of ions at pH 6.5 which exhibit complete miscibility in solid crystalline as well as in liquid crystalline. The mixture studied is the most frequent combination in biological membranes and may be a start point for further studies about more complex lipid mixtures with functional biology importance.We propose temperature-dependence zeta potential (ZP) measurements as a method of screening of the phase transition temperatures of lipid mixtures, because of its high sensibility and the low lipid mass required, such as 70% less than necessary in conventional calorimeters.Differential Scanning Calorimetry (DSC) allowed the validation of zeta potential as a method for studying the phase transition temperature and temperatures interval phase transition of lipid mixtures. Slow scanning rates during ZP measurements keep the sample close to thermal and thermodynamic equilibrium, allowing the precise determination of the phase diagram.In this work we fitted data obtained from ZP and DSC studies with different mathematical models, to estimate transition temperatures for different compositions of mixtures DPPC-DMPC. Results obtained from ZP were in good agreement with those from DSC.