AbstractThe normal modes have been calculated for structures having the dihedral angles of the four β‐turns of insulin. Frequencies are predicted in the amide I region near 1652 and 1680 cm−1. The former overlaps the α‐helix band at 1658 cm−1in the Raman spectrum, while the latter accounts for the hitherto unassignable band at 1681 cm−1. Calculated amide III frequencies extend above 1300 cm−1, providing a compelling assignment of the 1303‐cm−1band in insulin and similar bands in other