Protective effect caused by the exopolymer excreted by Pseudoalteromonas antarctica NF3 on liposomes against Triton X-100

The capacity of the glycoprotein (GP) excreted by Pseudoalteromonas antarct ica NF3 to protect phosphatidylcholine (PC) liposomes against the action of Triton X-100 was studied in detail. Increasing amounts of GP assembled wit h liposomes resulted in a linear increase in the effective surfactant-to-PC molar ratios needed to produce the same alterations in liposomes and in a linear fall in the surfactant partitioning between the bilayer and the aque ous phase. Thus, the higher the proportion of GP assembled with liposomes t he lower the surfactant ability to alter the permeability of vesicles and t he lower its affinity with these bilayer structures. In addition, increasin g GP proportions resulted in a progressive increase in the free surfactant concentration (Sw) for the same surfactant-liposome interaction step. The f act that Sw was always lower than the surfactant critical micelle concentra tion indicates that the interaction was mainly ruled by the action of surfa ctant monomers, regardless of the amount of GP assembled.