In the extended amide III region, one finds the "classical" amide III vibration of the peptide groups, which is an in-phase combination of the N-H in-plane bending and the C-N stretching vibration, as well as two C α -H bending vibrations. However, these three vibrations are strongly coupled, and furthermore couple with the corresponding vibrations of other residues, resulting in delocalized extended amide III vibrations. Previously, it was shown that by performing a localization of normal modes 61 in the extended amide III region, a local-mode picture can be recovered, in which the local-mode frequencies as well as their harmonic coupling constants can be directly related to the backbone dihedral angles. While this structural dependence is difficult to exploit for extracting structural information from conventional, one-dimensional vibrational spectra, 62 2D-IR spectra sensitively depend on these vibrational couplings between local modes.