Gas-phase spectroscopy and anharmonic vibrational analysis of the 3-residue peptide Z-Pro-Leu-Gly-NH2 by the laser desorption supersonic jet technique

► UV, IR and hole-burning spectra of a tri-peptide Z-PLG-NH2 were measured in a jet. ► The laser desorption technique was used to evaporate the peptide. ► The conformers were detected but the population is mainly distributed to a single conformation. ► MD simulations and DFT calculations reproduced the IR spectrum except for NH stretch. ► Anharmonic vibrational analysis VQDPT reproduced the splitting of the NH stretch.