Linear-Polarized IR-Spectroscopic and Structural Elucidation of Glycyl-L-Phenylalanyl-Glycine Hydrochloride Monohydrate

As a part of our spectroscopic and structural elucidation of small peptides, their salts and metal complexes, the polarized IR-spectroscopic and structural elucidation of the protonated form of glycyl-L-phenylalanyl-glycine as hydrochloride monohydrate (H-Gly-Phe-Gly-OHxHClxH2O) is reported. The obtained structure of the protonated tripeptide is supported by quantum chemical ab initio calculations at UHF level of theory and 6-31++G**, showing only one stable conformer with two intermolecular NH3 +…OH2 and (C=O)OH…OH2 hydrogen bonds. The Nterminus amide O=C-N-H amide fragment is flat trans-configured with a dihedral angle value of 179.0(7)°, while the corresponding group at Cterminus is with transoide-configurated and value of the dihedral angle of 151.1(3)°, respectively. In addition data of 1H- and 13C magnetic resonance spectroscopy (NMR), thermogravimetry (TGA), differential scanning calorimetry (DSC) and high performed liquid chromatography (HPLC) with tandem mass spectrometry (HPLC-MS/MS) as presented.