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

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

Córdoba

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

Sociedad Argentina de Biofísica

Antimicrobial peptides (AMPs) are naturally-occurring molecules that exhibit strong antibiotic properties against numerous infectious bacterial strains. Because of their unique mechanism of action, they have been touted as a potential source for novel antibiotic drugs. The AMPs act on cell membranes causing cell lysis or alteration of the membrane topology. We present a theoretical-experimental study on a novel series of AMPs interacting with vesicles composed of dioleoylphosphatidylcholine (DOPC) and dioleoylphosphatidylglycerol (DOPG). Our research primarily focuses on elucidating the molecular-level mechanism of action of these peptides. We experimentally assessed various physicochemical parameters that influence their antimicrobial activity, including charge, secondary structure, hydrophobicity, amphipathicity, and polarity. We conducted biophysical characterization of the peptides employing various techniques, such as circular dichroism (CD), linear dichroism (LD), infrared spectroscopy (IR), dynamic light scattering (DLS), and fluorescence spectroscopy. To complement these experimental studies, we performed molecular simulations using coarse-grain calculations, aiming to simulate the same systems that were examined experimentally. Both theoretical and experimental results indicate that the mechanism of action is primarily a surface-level phenomenon. It does not necessitate peptide internalization to exert their antimicrobial effects. This represents a clear distinction from proposed mechanisms of action for larger peptides, such as pore formation, carpet formation, or the toroidal mechanism. Furthermore, our findings underscore the significance of achieving a threshold peptide concentration to elicit their biological effects. In fact, the manner in which peptides with charge +4 accommodates on the vesicle's surface aligns with the theory of raft formation, which is supported by previous experimental and theoretical research.