title: A solid-state 17O NMR study of L -phenylalanine and L -valine hydrochlorides.
abstract: We have presented an experimental investigation of the oxygen-17 chemical shielding (CS) and electric-field-gradient (EFG) tensors for alpha-COOH groups in polycrystalline amino acid hydrochlorides. The 17O CS and EFG tensors including the relative orientations between the two NMR tensors are determined in [17O]-L-phenylalanine hydrochloride and [17O]-L-valine hydrochloride by the analysis of the 17O magic-angle-spinning (MAS) and stationary NMR spectra obtained at 9.4, 11.7, 16.4, and 21.8 T. The quadrupole coupling constants (CQ) and the span of the CS tensors are found to be 8.41-8.55 MHz and 7.35-7.41MHz, and 548-570 ppm and 225-231 ppm, for carbonyl and hydroxyl oxygen atoms, respectively. Extensive quantum chemical calculations using density functional theory (DFT) have been also carried out for a hydrogen-bonding model. It is demonstrated that the behavior of the dependence of hydrogen-bond distances on 17O NMR tensors for the halogen ions is different from those for the water molecule.
authors.affiliation: National Institute for Materials Science, 3-13 Sakura, Tsukuba, Ibaraki 305-0003, Japan. YAMADA.Kazuhiko@nims.go.jp
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Yamada
authors.forename: Tadashi
authors.initials: T
authors.lastname: Shimizu
authors.forename: Shinobu
authors.initials: S
authors.lastname: Ohki
authors.forename: Toshio
authors.initials: T
authors.lastname: Yamazaki
mesh_terms: D006851:Hydrochloric Acid / Q000737:chemistry* / Q000378:metabolism; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy / Q000379:methods / Q000592:standards*; D008956:Models, Chemical; D015394:Molecular Structure; D010103:Oxygen Isotopes; D010649:Phenylalanine / Q000737:chemistry* / Q000378:metabolism; D014633:Valine / Q000737:chemistry* / Q000378:metabolism
chemical_list: D010103:Oxygen Isotopes; D010649:Phenylalanine; D014633:Valine; D006851:Hydrochloric Acid