The cationic acrylate polymer Eudragit((R)) E100 (E100) produces a biphasic effect on the stability of casein micelles disrupting their internal structure (SF. Ausar et. al., J. Agric. Food Chem. 2003,51, 4417). These results suggested that this polymer could have some amphipathic character. Therefore, in this study the polymer was characterized with respect to its interaction with different amphipathic systems (bile-acid micelles, lipoproteins and liposomes), cell membranes (red blood cells) and virus membranes (Herpes simplex type 2 virus). As with caseins, a biphasic effect was served with bile acids with a precipitation phase at low polymer/bile acid ratio and a solubilization phase when the polymer concentration was increased. Upon interaction with man plasma, an important reduction in cholesterol and glycerides was observed upon remotion of E100 by a rise in pH to 8.5 and centrifugation. In agreement with this finding; important reduction in plasma lipoproteins was observed oh its treatment with E100 and further remotion by pH rise and centrifugation: However, the amount of the major protein components of human plasma and; the activity of several enzymes and antibodies were not affected by their treatment with E100. The membrane-destabilizing properties of E100 were confirmed by its lytic activity on liposomes and red blood cells and by an important antiviral effect of E100 on Herpes simplex virus type 2. Altogeather, these results show that, despite its water solubility and cationic character, E100 displays a signigicative amphipathis and membrane-destabilizing character with potential biotechnological applications. <GRAPHIC> Native-PAGE of human plasma lipoproteins after treatment with E100.