Next, we measured the helicity of the N-terminally acetylated hydrocarbon-stapled peptides using circular dichroism spectroscopy (CD). In solution, all stapled peptides NIP-2-5-Ac exhibited the characteristic α-helical conformation with two negative minima at wavelengths of 208 nm and 222 nm (Fig. ). In contrast, all linear peptides (NIP-WT-Ac, NIP-1-Ac and NIP-MUT-Ac) did not show much helical character confirming that stapling increases helicity. The highest affinity stapled peptide NIP-2-Ac has the highest helicity (28%) compared to all other peptides.