Synergistic interactions between antimicrobial peptides magainin 2 and PGLa

We suggest to measure the depth of penetration of two cationic antimicrobial peptides, namely magainin 2 (mag2) and PGLa, added separately and as an equimolar cocktail on single supported lipid bilayers. These peptides are known to exhibit a strong synergetic activity on living organisms but very important questions remain about their structure-function relationship. In particular, we want to know if the interaction between the different molecular systems leads to changes in the bilayer penetration depth. Membranes will be made of lipid mixtures mimicking biological systems (POPE/POPG 3/1, POPC/POPG 3/1 and POPE/POPG 1/3) that will permit to address the question of the role of membrane composition (i.e. POPE vs POPC) and to analyse the effect of anionic lipid concentration. While 25 to 30% of POPG represent well membranes of E. coli much higher lipid content can be encountered with Gram-positive bacterial membranes. 5 days of beamtime on INTER or 6 days on OFFSPEC are requested for this study.