Molecular response and cooperative behavior during the interactions of melittin with a membrane: dissipative quartz crystal microbalance experiments and simulations.

The molecular-level interactions of an antimicrobial peptide melittin with supported membrane were studied by the combination of dissipative quartz crystal microbalance (QCM-D) experiments and computer simulations. We found the response behavior of lipids upon peptide adsorption greatly influence their interactions. The perturbance and reorientation of the lipid in liquid phase facilitate the insertion of melittin in a trans-membrane way, but in solid phase, asymmetrical membrane disruption happens. Apart from the lipid state, the local peptide-to-lipid ratio also affects the insertion capacity of melittin. When the local peptide number density is high, adjacent peptides can cooperatively penetrate into the membrane. This observation explains the occurrence of the conventional "carpet" mechanism.