The geometries of all initial molecular structures were optimized using density-functional theory (DFT) with the Turbomole V7.6 program package 67 (Turbomole V7.1 for the polyalanine-15 structures) employing the BP86 exchange-correlation functional and the def2-TZVP basis set. Harmonic vibrational frequencies and normal modes were then calculated using the SNF program from the MoViPac suite. Both steps were automated using our PyADF scripting framework. All vibrational spectra have been calculated for the non-deuterated structures.