These differences in coupling constants are explicitly revealed in the 2D-IR spectra. Calculated 2D-IR spectra for three exemplary structures from the α-helix and β-strand regions, respectively, are shown in Fig. and. The full sets of calculated spectra for all considered structures are shown in the Supporting Information (see Figs. and). For the two different structural motifs, the calculated 2D-IR spectra show very distinctive patterns, with the diagonals reflecting the one-dimensional spectra discussed above. For the structures from the α-helix region, the two classical amide III vibrations (normal modes 3 and 4) show the strongest diagonal peaks, with an intense cross-peak between them. For the structures from the β-strand region, this cross-peak is absent. However, the diagonal peaks corresponding to the C α -H bending vibrations (normal modes 1 and 2) are now clearly visible, and there are strong cross peaks between those and the classical amide III vibrations, i.e., between normal . We find that in all three cases, the classical amide III vibrations lie up to a wavenumber of around 1250 cm -1 , whereas the C α -H bending vibrations are found between ca. 1260 cm -1 and 1340 cm -1 , in qualitative agreement with the results for the dipeptide model. The 2D-IR spectrum for the α-helical polyalanine-10 has a strikingly low intensity com- pared to the β-strand structure, with the classical amide III band as its most intense peak.