Vibrational analysis of peptides, polypeptides, and proteins. XXI. β‐Calcium‐poly(L‐glutamate)

The observed Raman and ir spectra of Ca‐poly( L ‐glutamate) in the β conformation have been analyzed by means of a normal mode calculation. The force field for the main chain was transferred without refinement from β‐poly( L ‐alanine), yet it provides a good prediction of the observed bands and, in particular, explains subtle differences in the spectra of these two β‐sheet structures. Main‐ and side‐chain modes are well characterized, and the dependence of the amide III frequency on side‐chain composition is again demonstrated.