POLYMORPHISM OF PALMITOYLCERAMIDE MONOLAYERS: THERMODINAMIC AND TOPOGRAPHYC STUDY

MARIA L. FANANI; BRUNO MAGGIO

Los Cocos, Córdoba

Congreso; XXXVIII Reunión Anual de la Sociedad Argentina de Biofísica: Biofísica de Sistemas Autoorganizados; 2009

Sociedad Argentina de Biofísica

Ceramide (Cer) is a simple sphingolipid that form Cer-enriched (liquid-condensed) domains when mixed with phospholipids or more complex sphingolipids like sphingomyelin. In addition, Cer accumulation in cell membrane has important physiological consequences that are associated to its capacity as membrane reforming lipid. Pure Cer aqueous dispersion shows a phase transition peak by DSC at high temperatures (≈90) and a condensed behaviour in monolayers at room temperature. Furthermore, evidences of a polymorphic behaviour indicating the existence of more than one condensed phase was proposed previously [1]. In this work we deep in the study of the polymorphic behaviour of a chemically defined Cer, palmitoylceramide (pCer) using langmuir balance measurements. Both isobaric and isothermal studies reveal a main (first order) transition from liquid-expanded (LE) to liquid-condensed (LC) states in the range of 40-50°C and a diffuse LC-LC transition at the room temperature range. Brewster Angle Microscopy reveals gas / liquid-condensed coexistence region that explain the unusual behaviour of pCer monolayers at low temperatures. [1] J.V.Busto, M.L.Fanani, L.De Tullio, J.Sot, B.Maggio, F.M.Goni, and A.Alonso, Coexistence of immiscible mixtures of palmitoylsphingomyelin and palmitoylceramide in monolayers and bilayers, Biophys J (2009) In Press.