Glycosaminoglycans (GAGs) are important constituents of the extracellular matrix of microorganisms, animals and plants. These are large polymers formed by mono, di or oligo-saccharides bounded by glycosidic linkages. These polyelectrolyte may have a variety of functional groups along his chain. Within these polysaccharides can find functionalized dextran sulfate (DS, negatively charged), and di-ethyl-amino-ethyl dextran (DEAE, positive polysaccharide). Although polysaccharides (negatively charged) have been associated with biological function into the membrane and, through it, their specific role is not known, and it has been reported that its presence affects the dynamics of lipids and proteins. The aim of this work is to study how the presence of different polysaccharides modifies the rheological properties of model membranes. This will be used as models of membrane lipid monolayers of dimyristoyl phosphatidyl glycerol (DMPG) and diPALMITOILphosphatidylcholyne (DPPC).The polysacharyd studied were DS of high (DSA) and low (DSB) sulphate content, and di-ethyl-amino-ethyl dextran (DEAE). DMPG and DPPC films were formed over a subphase CaCl2 (10 mM) and NaCl (145mm), under this conditions both lipids have a phase transition from liquid expanded to liquid condensed phase- about 15mN / m and 7,5 mN/m for DMPG and DPPC, respectively. When the monolayer is formed in the presence of DSB, any changed in the isotherm of both lipids were found. In the case of DSA the effect on the isotherm depends of the lipid. In contrast, in presence of DEAE the expanded phase of both lipids was stabilized. Whit the aim of completes the caracaterization of the system the diffusion coefficients of condensed domains and the viscosity of the expanded phase were measure under all conditions.
