Dynamics and topology of phospholipase-modified lipid interfaces

MARIA L. FANANI; BRUNO MAGGIO

Salta

Simposio; XXXIX Reunión Anual de la Sociedad Argentina de Biofísica realizado conjuntamente con la III Latinamerican Protein Society Meeting; 2010

Sociedad Argentina de Biofísica

The dynamics of lipid membranes that show phase coexistence has the potential capacity to regulate other chemical and physical processes that take place in the lipidic environment. The fast action of phospholipases adsorbed to the membrane interface regulates and are in turn regulated by the structure and dynamics of the membrane. Sphingomyelinase degrades sphingomyelin to the highly hydrophobic lipid ceramide. This compositional perturbation brings about important consequences for the structural dynamics since the production of ceramide occurs over a time scale close to that of other lipid reorganization processes such as lipid de-mixing and domain formation, therefore involving out-of-equilibrium restructuring of the lipid interface. We focused on the structure and dynamics of both ceramide-enriched condensed domains and cholesterol-enriched liquid-ordered (putatively raft-like) domains and on the perturbation that sphingomyelinase induces on these surfaces. For approaching these studies, lipid monolayers were used. This technique brings detailed thermodynamic information of the lipid ensemble while keeping control of molecular parameters like molecular area, composition, dipolar properties and surface pressure. Additionally, we employed fluorescence and Brewster angle microscopy applied to monolayers which afford accessibility to the structural topology of the coexisting phases at the surface. Acknowledgments: Supported by: CONICET, FONCyT, SECyT-UNC, ACC-MinCyT (Córdoba).