The bending rigidity of phospholipid monolayers in presence of an antimicrobial frog peptide studied by X-ray grazing incidence diffraction

Peptide secretion by living organisms constitutes an integral response process exploited by natural immune systems. In this work we present a model study and insight into this process reporting the thermodynamic and structural effects induced in phospholipid monolayers due to peptide insertion into the layer. Synchrotron X-ray radiation is combined with the Langmuir technique and exploited to form 'lipid-peptide' monolayers and probe the physical characteristics of the fundamental biological process of 'peptide secretion'. Our experiments show that the insertion of peptides in the phospholipid layer has adverse effects on the elastic properties of the layer manifested through the bending rigidity.