Main phase transitions in supported lipid single-bilayer

We have studied the phase transitions of a phospholipidic single- bilayer supported on a mica substrate by realtime temperature- controlled atomic force microscopy. We show the existence of two phase transitions in this bilayer that we attribute to two gel ( L-beta)/fluid (L-alpha) transitions, corresponding to the independent melting of each leaflet of the bilayer. The ratio of each phase with temperature and the large broadening of the transitions' widths have been interpreted through a basic thermodynamic framework in which the surface tension varies during the transitions. The experimental data can be fit with such a model using known thermodynamic parameters.