Protective effect caused by the exopolymer excreted by Pseudoalteromonas antarctica NF(3) on liposomes against the action of octyl glucoside

Abstract

The capacity of the glycoprotein (GP) excreted by Pseudoalteromonas antarctica NF(3), to protect phosphatidylcholine (PC) liposomes against the action of octyl glucoside (OG) was studied in detail. Increasing amounts of GP assembled with liposomes resulted for the same interaction step in a linear increase in the effective surfactant to PC molar ratios (Re) and in a linear fall in the surfactant partitioning between bilayer and the aqueous phase (partition coefficients K). Thus, the higher the proportion of GP assembled with liposomes the lower the surfactant ability to alter the permeability of vesicles and the lower its affinity with these bilayer structures. In addition, increasing GP proportions resulted in a progressive increase of the free surfactant concentration (S(W)) needed to produce the same alterations in liposomes. The fact that S(W) was always lower than the surfactant critical micelle concentration indicates that the interaction was mainly ruled by the action of surfactant monomers, regardless of the amount of assembled GP.