The calculated 2D-IR spectra for these structures of polyalanine-15/16 are shown in Fig. . These larger and more distorted structures feature considerably more peaks in the one-dimensional infrared spectra, leading to overall more complex 2D-IR spectra. Never-theless, these largely follow the pattern already observed for the idealized structures. For the α-helical polyalanine-15, the 2D-IR spectrum has a rather low intensity, with the classical amide III vibration giving rise to the strongest peak. The C α -H bending vibrations as well as their cross-peaks with the classical amide III vibrations gain some intensity compared to the idealized structures, but remain rather weak. In contrast, For the β-strand and the β-hairpin, the C α -H bending vibrations show a strong peak on the diagonal as well as visible cross-peaks with the classical amide III vibrations. Compared to the idealized structures, these are somewhat weaker, but can still serve to clearly distinguish the α-helical and β-strand structures.