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.