GLYCOPROTEIN EXCRETED BY PSEUDOALTEROMONAS-ANTARCTICA NF3 AS A COATING AND PROTECTIVE AGENT OF LIPOSOMES AGAINST SODIUM DODECYL-SULFATE

The ability of an exopolymer of glycoproteic character (GP) excreted b y a new Gram-negative species Pseudoalteromonas antarctica NF3, to coa t phosphatidylcholine (PC) liposomes and to protect; these bilayers ag ainst the action of the sodium dodecyl sulfate (SDS) surfactant was in vestigated. Transmission electron microscopy micrographs of freeze fra ctured liposome/GP aggregates reveal that the addition of GP to liposo mes led to the formation of a film (polymer adsorbed onto the bilayers ) that tightly coated PC bilayers. The complete coating was achieved a t a PC:GP weight ratio of about 9:1. Higher GP amounts resulted in a g rowth of this film, which exhibited at the highest GP proportion (50% of GP in weight) a multilayered structure. An increasing resistance of PC liposomes to be affected by SDS at both subsolubilizing and solubi lizing levels occurred as the proportion of GP in the system rose, alt hough this protective effect was more effective at low GP proportions (PC:GP weight ratios from 9:1 to 8:2). Although a direct dependence wa s found between the growth of the enveloping structure and the resista nce of the coated liposomes to be affected by SDS, the best protection occurred when this structure was a thin film (thickness of about 20-2 5 nm for a PC:GP weight ratio ranging from 9:1 to 8:2).