Fig. 3. Conformational state of the synthetic neck peptide Kn1. (A) The CD spectrum of the peptide Kn1 at varying pH values shows that an acidic environment below pH 4.5 induces an α-helical conformation, indicating the importance of protonated glutamic acid residues. (B) The ellipticity ratio [Θ]₂₂₂/[Θ]₂₀₈ of 1.03 in 50 mM phosphate buffer at pH 3, 20°C, indicates a coiled-coil formation, which is disrupted by increasing amounts of TFE, as seen by the sigmoidal decrease of [Θ]₂₂₂/[Θ]₂₀₈ to 0.96.