Theoretical and Experimental Study on the Mechanism of Action of New Short Sequence Cationic Antibacterial Peptides

FRIGINI, EZEQUIEL N; ADARVEZ FERESIN, CAMILA; PORASSO, RODOLFO D.; PANTANO, SERGIO; BEKE-SOMFAI, TAMÁS; LÓPEZ CASCALES, JOSÉ JAVIER; ENRIZ, RICARDO D.

Córdoba

Congreso; LI Reunión Anual de la Sociedad Argentina de Biofísica; 2023

IIByT- CONICET ? UNC

Antimicrobial peptides (AMPs) are naturally-occurring molecules that exhibit strongantibiotic properties against numerous infectious bacterial strains. Because of theirunique mechanism of action, they have been touted as a potential source for novelantibiotic drugs. The AMPs act on cell membranes causing cell lysis or alteration of themembrane topology. We present a theoretical-experimental study on a novel series ofAMPs interacting with vesicles composed of dioleoylphosphatidylcholine (DOPC) anddioleoylphosphatidylglycerol (DOPG). Our research primarily focuses on elucidating themolecular-level mechanism of action of these peptides. We experimentally assessedvarious physicochemical parameters that influence their antimicrobial activity, includingcharge, secondary structure, hydrophobicity, amphipathicity, and polarity. We conductedbiophysical characterization of the peptides employing various techniques, such ascircular dichroism (CD), linear dichroism (LD), infrared spectroscopy (IR), dynamic lightscattering (DLS), and fluorescence spectroscopy. To complement these experimentalstudies, we performed molecular simulations using coarse-grain calculations, aiming tosimulate the same systems that were examined experimentally. Both theoretical andexperimental results indicate that the mechanism of action is primarily a surface-levelphenomenon. It does not necessitate peptide internalization to exert their antimicrobialeffects. This represents a clear distinction from proposed mechanisms of action for largerpeptides, such as pore formation, carpet formation, or the toroidal mechanism.Furthermore, our findings underscore the significance of achieving a threshold peptideconcentration to elicit their biological effects. In fact, the manner in which peptides withcharge +4 accommodates on the vesicle´s surface aligns with the theory of raft formation,which is supported by previous experimental and theoretical research.