Interaction of the cationic peptide bactenecin with phospholipid monolayers at the air - Water interface: I interaction with 1,2-dipalmitoyl-sn-glycero-3- phosphatidilcholine

In this work we have investigated the influence of NaCl on the adsorption of the antimicrobial cationic peptide bactenecin in the monolayer of 1, 2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) at the air-water interface, as a function of NaCl concentrations in the subphase. We show that the effect of the salt concentration on DPPC monolayers is a monotonic decrease of the liquid-condensed-liquid-expanded (LC-LE) coexistence region. By contrast, the effect of the bactenecin adsorption at the DPPC monolayer not only removed the LC-LE coexistence region plateau, but also shifted the DPPC isotherms to higher pressures and increased the compressibility of the DPPC/bactenecin monolayers with respect to the pure DPPC monolayer around the LC phase. Analysis of the domain structure, obtained by Brewster angle and atomic force microscopes, indicates that the salt concentration in the subphase builds an electrostatic barrier, increasing the rigidity of DPPC monolayers and limiting the bactenecin adsorption at the LC-LE phase coexistence. © 2009 American Chemical Society.

Adsorption; Air; Amines; Atmospheric temperature; Dyes; Electron energy levels; Liquids; Monolayers; Phospholipids; Sodium chloride; 1 ,2-dipalmitoyl-sn-glycero-3-phosphocholine; Air water interfaces; Atomic force microscopes; Brewster angle; Cationic peptides; Coexistence region; Domain structure; DPPC monolayers; Electrostatic barriers; Monotonic decrease; NaCl concentration; Phase co-existence; Phospholipid monolayers; Salt concentration; Subphase; Phase interfaces

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