Thermal Fluctuation and Elasticity of Lipid Vesicles Interacting with Pore-Forming Peptides

The thermal fluctuation and elasticity of dioleoyl-phosphocholine large unilamellar vesicle interacting with pore-forming peptide, melittin, were investigated by neutron spin-echo measurements. The relaxation behavior of the membrane fluctuation with different peptide to lipid molar ratio P/L can be divided into three regions, resulting from characteristic changes of the effective bending modulus (kappa) over tilde of the membrane which includes the effects of internal dissipation within the membrane. At low P/L, melittin is adsorbed parallel to the surface of membrane and (kappa) over tilde decreases significantly due to perturbation of hydrocarbon chain packing. At a critical P/L, melittin forms pores in the membrane and (kappa) over tilde starts to increase slightly due to high pore rigidity. At higher P/L where the repulsive interpore interaction becomes significant, (kappa) over tilde increases rapidly.