?Interaction of polysaccharides with lipid monolayers and the consequential modulation of the film properties?

C. I. CÁMARA, N. WILKE

Puerto Iguazú

Conferencia; 56th International Conference on the Bioscience of lipids; 2015

Polysaccharides have been associated with different biological functions by binding to the membrane, but their specific role is not known. A probably very important role of these polymers is the regulation of the membrane dynamics, as their presence affects the dynamics of lipids and proteins. Therefore, the aim of this work was to study how the presence of different polysaccharides modifies the rheological properties of model membranes. Here we studied the affinity and consequences of the interaction of dextran sulfate (DS, negatively charged), and di-ethyl-amino-ethyl dextran (DEAE, positive charged) with DPPC and DMPG monolayers. DMPG and DPPC films were formed over a subphase containing CaCl2 (10 mM), NaCl (145mm) and the polysaccharide and the effect of the polymer on the corresponding phase transitions was studied by compression isotherms while the surface was observed with Brewster Angle Microscopy. The film viscosity was determined by single particle tracking. Our general conclusions are that electrostatic interactions play an important role in the polymer-membrane interaction, in agreement with results on the literature. The polymers interact with the DMPG monolayers without incorporating into the film, but forming an underlayer. The presence of this underlayer increases the shear viscosity of the interface, thus affecting the process of domain nucleation and thereby, the domain size and shape. In the presence of the polymer, the lipid film adopts a polymer-like behavior: the whole film (polymer + lipid) is highly compressible and very viscous, which are characteristics of polymer films.