Lipid discrimination in phospholipid monolayers by the antimicrobial frog skin peptide PGLa. A synchrotron X-ray grazing incidence and reflectivity study.

We present a first study using synchrotron grazing incidence diffraction and X-ray reflectivity measurements on mixed phospholipid/peptide monolayers at the air/water interface. The thermodynamic properties of the pure and mixed monolayers were characterized using the classical film balance technique. Surface pressure/potential-area isotherms showed that the antimicrobial frog skin peptide PGLa formed a very stable monolayer with two PGLa molecules per kinetic unit and a collapse pressure of ~22 mN/m.