Study of antibiotic peptide interaction with bacterial model membrane systems by GIXOS

Bacterial membranes are interesting as case of study of lipid interaction in biomembranes as they are formed by a few classes of phospholipids. In addition, antibiotic peptides produced by members of all kingdoms of life affect membrane permeability as a principal part of the mechanism of action. In the present work we explored the role of membrane composition of Gram positive model systems on the interaction with the bacteriocin enterocin CRL35 by means of Langmuir monolayers and Off-Specular X-Ray diffraction at grazing incidence (GIXOS). Lipid mixtures used were PG:PE 80:20 and CL:PG:PE 40:40:20, in order to study Gram positive mimics and the role of cardiolipin in membrane properties and peptide interaction. Affinity of enterocin to lipid films was assessed by calculating exclusion surface pressure and monolayer structure mainly by determining the minimum of the first lobe of GIXOS pattern for getting insight of monolayer thickness. Results indicate that cardiolipin modulates affinity of enterocin towards bacterial lipids and diminishes monolayer thickening upon peptide interaction. (author)