The one-dimensional infrared spectra clearly demonstrate the large structural sensitivity of the vibrations in the extended amide III region (see also Ref. 60), but the large variations of peak positions and intensities within the two considered structural motifs complicate a use for a direct structural assignment. However, when switching to a local-mode picture, the relationship between local-mode frequencies as well as harmonic coupling constants and the backbone dihedral angles becomes more direct. For a detailed discussion, we refer to Ref. 60. Fig. visualizes the mean values and standard deviations of the local-mode frequencies and the harmonic coupling constants for the structures considered in the α-helix and in the β-strand region (see Tables and in the Supporting Information for underlying data).