Figure 4: Secondary structure analysis of incorporated M2 proton channels in the lipid layers of AuCLs. (a) Illustration of an M2 protein, having a folded structure, in a lipid bilayer environment. The M2 protein has an inherent α-helical conformation in cellular membrane environments. (b) Circular dichroism (CD) spectra of M2 proteins with citrate-capped AuNPs (black), incubated with AuCLs (blue), or after eliminating excess M2 protein in supernatant (red). Strong negative peaks appear at wavelengths of 208 nm and 222 nm, which represent an α-helix conformation.