To assess the accuracy of vibrational exciton models, we constructed a test set of six polypeptides that cover a range of different secondary structure elements (see Fig. ). For each of these six structures, classical molecular dynamic (MD) simulations were performed for the polypeptides solvated in water, and from each of these MD trajectories, eleven snapshots were extracted. For both the isolated polypeptide structures extracted from these snapshots as well as for the polypeptides solvated in water, partial geometry optimizations were performed using density-functional theory (DFT). For the solvated polypeptides, a simple QM/MM setup in which explicit water molecules contribute classically was employed. Details on the molecular dynamics and the subsequent quantumchemical calculations are given in the Section "Computational Details" at the end of this article. This resulted in eleven structures per test case, except for the (Ala) 15 β-strand and Trpzip2, where the geometry optimizations failed for one snapshot and thus only ten structures could be optimized.