Membrane Binding Kinetics of Amphipathic Helical Peptides from Hepatitis C Virus: Quartz Crystal Microbalance with Dissipation Monitoring

Abstract Using quartz crystal microbalance with dissipation monitoring (QCM-D), we investigate the kinetics of attachment of three amphipathic helical (AH) peptides to a supported POPC lipid bilayer. The focus is on the peptides derived from hepatitis C virus (HCV) nonstructural proteins: the N-terminal AH of NS5A and two helices (AH1 and AH2) from NS4B. NS5A AH exhibits conventional monotopic insertion with rapid frequency decrease, minimal dissipation increase, and immediate stabilization, indicating rigid interfacial embedding and bilayer immobilization without formation of a viscoelastic overlayer. NS4B AH1 displays monotonic adsorption similar to NS5A but with moderately elevated dissipation, consistent with cooperative lateral peptide–peptide interactions superimposed on membrane insertion. In contrast, NS4B AH2 shows strongly non-Langmuirian behavior. At low concentrations (3.25–6.5 μM), it forms a highly dissipative, hydrated interfacial layer dominated by peptide aggregation. Above a threshold at 6.5 μM, there is transition toward a compact membrane-engaged state with reduced dissipation and late-stage structural relaxation. This aggregation-to-insertion transition reflects a shift in dominant interaction from lateral self-association to cooperative membrane coupling. These observations have been interpreted by employing a phenomenological kinetic model implying three peptide surface states representing disordered aggregates and compact membrane-bound domains.