Advances in the characterization of antimicrobial peptide P8.1 interactions with anionic lipid vesicles

Abstract

Antimicrobial peptides (AMPs) are promising complements to antibiotics, yet theirmembrane‑level actions remain incompletely understood. We previously characterized theeffects of the “de novo” cationic AMP P8.1 on anionic lipid bilayers composed of DPPG (gelphase) or DLPG (fluid phase), showing that P8.1 binds both lipids but induces a higherlocal order and a tighter acyl‑chain packing in DLPG vesicles. Here, we furtherinvestigated P8.1-lipid interactions using dynamic light scattering (DLS), tryptophanfluorescence, Raman microscopy, and carboxyfluorescein (CF) leakage assays. DLSrevealed vesicle enlargement upon peptide binding. Trp fluorescence showed deeperinsertion of P8.1 in DLPG (larger Trp blue‑shift and lower acrylamide quenching). Ramanspectra showed an amide I shift of P8.1, supporting a random coil-to-α‑helix transitionupon lipid binding. Finally, P8.1 induced ~80% CF leakage in DLPG vesicles withinminutes. Altogether, these data indicate that P8.1 engages lipid phosphate groups andsubsequently modulates bilayer order in a phase- and mechanics-dependent manner,providing mechanistic insight into its antibacterial activity.