Fig. 5

Identification of vesicle rupturing process by AH peptide. AH peptide-vesicle interaction analysis. Changes in resonance frequency of oscillation (blue curve) and energy dissipation (red curve) were monitored by the QCM-D technique. All data were collected at the third overtone and normalized. a Intact vesicle adsorption on an oxidized gold surface. After 10 min of stabilization, lipid vesicles were added (arrow 1). After 50 and 55 min, buffer washes were performed in order to test the stability of the film (arrows 2 and 3, respectively). b AH peptide promotes vesicle-to-bilayer transformation. At 60 min (arrow 4), AH peptide was added to the intact vesicle layer on the gold surface. After 120 and 140 min, buffer washes were again performed (arrows 5 and 6, respectively). c NH peptide has no effect on the intact vesicle platform. Identical experiments to those described in Fig. 8b were performed with the control NH peptide, and demonstrated that the NH peptide does not affect the properties of the intact vesicle layer. Morphological effects of AH peptide-mediated vesicle rupture. AFM imaging characterized the vesicle rupturing process on gold. All images are presented in height mode. d Oxidized gold surface. e Adsorbed layer of intact lipid vesicles on the gold surface. f Planar bilayer self-assembles after treatment with the AH peptide. Modeling QCM-D responses for structural transformation from adsorbed vesicles to a planar bilayer. Identical experiments to those described in Fig. 8b were performed. g Resonance frequency responses at multiple overtones were recorded for the vesicle-to-bilayer transformation. h Corresponding energy dissipation responses were also recorded. i Change in film thickness was determined by application of the Sauerbrey equation to the QCM-D data. For comparison, we also present the thicknesses calculated from the Voigt-Voinova model for the intact vesicle layer (22 nm) and planar bilayer (4.4 nm). Note that n = 1 shows fundamental overtones (open squares), n = 3 shows third overtones (open circles), n = 5 shows fifth overtones (open triangles), and n = 7 shows seventh overtones (opposite triangles). Figure is adapted and modified from Refs. [40, 42]