Vibrational analysis of peptides, polypeptides and proteins. XII—fermi resonance analysis of the unperturbed ND stretching fundamental in polypeptides

We have obtained the spectrum of β‐poly(L‐alanine‐ND), and find three bands in the ND stretching region. By comparison with Fermi resonance analyses of deuterated derivatives of polyglycine I as well as with α‐poly(L‐alanine‐ND), we conclude that a three‐level Fermi resonance is involved in the β polypeptide, and that the unperturbed ND stretch fundamental occurs near 2428 cm −1 .