ACTIVE PENETRATION OF CHARGED PEPTIDES INTO MONOMOLECULAR FILMS OF DEEP ROUGH MUTANT LIPOPOLYSACCHARIDE

The active penetration of various positively charged substances into m onomolecular films of deep rough mutant lipopolysaccharide (ReLPS) has been investigated. In this study the antibiotic polymyxin B (PMB) sho ws the highest affinity to lipspolysaccharides and increases the area of ReLPS monofilms by 50%. It binds with a molar ratio of n [PMB/ReLPS ] approximate to 0.8 and neutralises the charge of the lipopolysacchar ide in the monofilm. In contrast, other highly positively charged subs tances are almost inactive. A two step mechanism for the interaction i s proposed. In the first step, electrostatic attraction leads to a wea k binding between the positively charged substance and the negatively charged lipid. In a second step, the lipophilic part of the substance is inserted into the membrane.