title: Both experimental and theoretical investigations of solid-state 17O NMR for L-valine and L-isoleucine.
abstract: We have presented an experimental investigation of the carboxyl oxygen NMR parameters for four distinct sites in l-valine and l-isoleucine. The carboxyl (17)O quadrupolar coupling constant, C(Q), and isotropic chemical shift, delta(iso), for these compounds are obtained by analyzing two-dimensional (17)O multiple-quantum magic-angle spinning (MQMAS) and/or 1D MAS spectra. The values of C(Q) and delta(iso) found to be in the range of 7.00-7.85 MHz, and 264-314 ppm, respectively. Extensive quantum chemical calculations at the density functional levels have been performed for a full cluster of l-valine molecules and a few theoretical models. The calculated results indicated that there was a correlation between the (17)O NMR parameters and C-O bond lengths, which was helpful for the spectral assignment. They also demonstrated that the torsion angle of l-valine plays an important role in determining the magnitudes of (17)O NMR parameters.
authors.affiliation: RIKEN Genomic Sciences Center, 1-7-22 Suehiro, Tsurumi, Yokohama 230-0045, Japan. kyamada@gsc.riken.jp
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Yamada
authors.forename: Takahiro
authors.initials: T
authors.lastname: Nemoto
authors.forename: Miwako
authors.initials: M
authors.lastname: Asanuma
authors.forename: Hisashi
authors.initials: H
authors.lastname: Honda
authors.forename: Toshio
authors.initials: T
authors.lastname: Yamazaki
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Hirota
mesh_terms: D007532:Isoleucine / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008968:Molecular Conformation; D010103:Oxygen Isotopes; D014633:Valine / Q000737:chemistry*
chemical_list: D010103:Oxygen Isotopes; D007532:Isoleucine; D014633:Valine