Phase transition behaviour in giant unilamellar vesicles containing ceramides

MATEOS DIEGO , CARRER DOLORES C

Puerto Madryn

Congreso; XLVI Reunion anual - Sociendad Argentina de Investigación en Bioquímica y Biología Molecular; 2010

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

Phase transition behaviour in giant unilamellar vesicles containing ceramides Diego Mateos,  Dolores C. Carrer, mateosdiego@gmail.com Instituto de Investigación Médica Mercedes y Martín Ferreyra (INIMEC – CONICET), Córdoba, Argentina It is generally plasma membrane lipids contribute to cellular processes, although very little is known regarding the underlying physical basis by which lipids accomplish this function, one hypothesis  is that the cell mebrane contain dynamic submicrometer domains  that are enriched in certain lipids , and these can change in size, composition  and stability in response to cues. There is evidence showing that also in complex cell membranes, the  tendency of certain lipid mixtures to phase separate is maintained, especially those containing cholesterol and a mixture of saturated and unsaturated lipids. We are particularly interested in the dynamics of the coexisting domains near the phase transition temperature as a function of composition, since previous data of ours suggests the possibility of these mixtures showing a critical point.When a multicomponent system aproaches  a critical point the two coexisting phases become identical and the system needs very litle energy to maintain inhomogeneous composition.This critical point depends mainly on de temperature and the composition.Our model system consists of  Giant Unilamellar Vesicles (GUVs) composed of dioleoylPC (DOPC)-Brain sphingomyelin (BSM)-Brain ceramide (BCer)-Cholesterol (CHOL), at different proportions BSM:BCer. We have characterized this system by means of  confocal fluorescence microscopy at different temperatures.