Label-free characterization of peptide-lipid interactions using immobilized lipodisks

Lipodisks, planar lipid bilayer structures stabilized by PEG-ylated lipids, were in the present study covalently bound and immobilized onto sensors for quartz crystal microbalance with dissipation monitoring (QCM-D) studies. It is shown that the modified sensors can be used to characterize the interaction of lipodisks with α-helical amphiphilic peptides with an accuracy similar to that obtained with well established fluorimetric approximations. The method presented has the great advantage that it can be used with peptides in their native form even if no fluorescent residues are present. The potential of the method is illustrated by determining the parameters describing the association of melittin, mastoparan X, and mastoparan with immobilized lipodisks. Both thermodynamic and kinetic analyses are possible. The presented method constitutes a useful tool for fundamental studies of peptide-membrane interactions and can also be applied to optimize the design of lipodisks, for example, for sustained release of antimicrobial peptides in therapeutic applications.