Local Pressure Changes in Lipid Bilayers Due to Adsorption of Melittin and Magainin-h2 Antimicrobial Peptides: Results from Computer Simulations

We performed a series of coarse-grained computer simulations in order to study how the placement of melittin and magainin-h2 antimicrobial peptides on the surface of the bilayer changes the local pressure profiles in the bilayer. The simulations were done using the NPT ensemble when the total stress on the bilayer was zero and also using the NP(z)AT ensemble, with a nonzero total stress. In the NPT ensemble, although the total stress was zero, each leaflet of the bilayer experienced a nonzero stress, and the stresses are equal by magnitude, but opposite in their direction. The observed stresses acting on the monolayers may cause the rupture of the monolayers to release the stress. Our simulations were done at different peptide to lipid ratio (P/L). When the P/L ratio was 1/50 there was no large difference in the local pressure profile for bilayers with melittin versus bilayers with magainin-h2. When simulations were performed in the NP(z)AT ensemble at P/L = 3/100 we observed a large difference in the pressure profiles in the bilayers with melittin peptides compared to the bilayer with magainin-h2. The observed in this case difference in stress may explain the difference in actions of melittin and magainin at high P/L.