The initial mechanism by which antimicrobial peptides target microbes occurs via electrostatic interactions; however, the mechanism is not well understood. We investigate the interaction of the antimicrobial peptide bactenecin with a 50:50. w:w% 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-dimyristoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (DMPG) phospholipid mixture at the air-water interface with different NaCl concentrations (0.01, 0.05, 0.1, 0.5. M) in the subphase. A larger shift of DPPC:DMPG isotherms was obtained for 0.1. M salt concentration at lower and higher pressures, demonstrating the influence of the negative charge of DMPG molecules and the screening of the electrostatic interaction by the salt concentration. Raman spectroscopy of monolayers demonstrated the presence of cysteine-cysteine bridges in bactenecin loops. The peptide adsorption in DPPC:DMPG monolayers observed by AFM images suggests a self-assembled aggregation process, starting with filament-like networks. Domains similar to carpets were formed and pore structures were obtained after a critical peptide concentration, according to the carpet model.
Bibliographical noteFunding Information:
The Consejo Nacional de Ciencia y Tecnologìa (CONACyT) is gratefully acknowledged for grants Apoy-Compl-2008-90345 and 83191. A.B.L.O. acknowledges a Ph.D. scholarship from CONACYT. We appreciate the technical assistance of Teresita Pesqueira to obtain Raman spectra and helpful discussions with Josué Juárez.
- Antimicrobial peptides
- Carpet model
- Raman spectroscopy