INTERACTION OF POLYMYXIN LOADED POLYPEPTIDE WITH BACTERIAL MEMBRANE MODELS

FEITO, FRANCISCO; MADRID, ROSSANA; DUPUY, FERNANDO G.

Congreso; XLIX Reunión Anual de la Sociedad Argentina de Biofísica; 2021

Sociedad Argentina de Biofísica

It is now known that the interaction of peptides with biological membranes is a key process in the study of the different cellular mechanisms and metabolic pathways necessary for cells to carry out their function, since this interaction can affect the properties of the lipid bilayer such as selective permeability and modulate curvature. The biological role of peptides in membrane interactions is determined by the charge present in the sequence of amino acids that form these biomolecules. Certain cationic polypeptides act as antimicrobial agents, altering the cell membrane of bacteria, due to the binding with the outer membrane in Gram-negative bacteria, finally causing their death, as is the case of the cyclic polypeptide, Polymyxin or also called Colistin B (Pmx). In this work we seek to gain knowledge about the mechanism of action of this antimicrobial peptide at the molecular level, as well as its effects on biological membranes, by studying different models of mimetic membranes using Langmuir- Blodgett phospholipid monolayers. The effect of pH and lipid composition on the interaction with polymyxin was studied by performing fixed-area Gibbs isotherms and Langmuir isotherms, measuring surface pressure and surface electric potential simultaneously. The results of this work indicate that pH modulates the surface activity of the peptide at clean interfaces and when interacting with negatively charged lipid monolayers. The insertion would be through a mechanism not yet elucidated, which is being studied.