Structural elucidation upon binding of antimicrobial peptides into binary mixed lipid monolayers mimicking bacterial membranes

Antimicrobial peptides (AMPs) kill microorganisms by causing structural damage to bacterial membranes. Different often require a different type and concentration of an AMP achieve full microbial killing. We hypothesise that the difference is caused membrane structure composition. Given complexities membranes, we have used monolayers binary DPPG/TMCL mixture mimic cytoplasmic Gram-positive bacteria DPPG/DPPE Gram-negative bacteria, where DPPG, TMCL DPPE stand for 1,2-dipalmitoyl- sn - glycero -3-phospho-(1′- rac -glycerol), 1′,3′-bis[1,2- dimyristoyl -3- phospho ]- -glycerol, -3-phosphoethanolamine, respectively. A Langmuir trough was specially designed control spread lipid facilitate neutron reflectivity measurements. Surface pressure-area isotherm analysis revealed all systems mix non-ideally, but mixing thermodynamically favoured. An increase in surface pressure encourages demixing, resulting phase separation formation clusters. Neutron measurements were undertaken study binding antimicrobial peptide G(IIKK) 4 -I-NH 2 (G ) monolayer mixtures at molar ratios 6/4 3/7, The results stronger penetration G monolayer, indicating greater affinity due electrostatic interaction more extensive into loosely packed film. This work helps explain how AMPs attack are discussed context other models antibacterial studies.