Polymorphism of palmitoyl-ceramide monolayers: thermodynamic and topographyc study

MARIA LAURA FANANI Y BRUNO MAGGIO

Los Cocos, Cordoba

Congreso; XXXVIII Reunion Anual de la Sociedad Argentina de Biofisica: Biofisica de Sistemas Autoorganizados.; 2009

Sociedad Argentina de Biofisica

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 (90C) 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 40-50C 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.