Both experimental and theoretical investigations of solid-state 17O NMR for L-valine and L-isoleucine.
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.
Yamada
Kazuhiko
K
RIKEN Genomic Sciences Center, 1-7-22 Suehiro, Tsurumi, Yokohama 230-0045, Japan. kyamada@gsc.riken.jp
Nemoto
Takahiro
T
Asanuma
Miwako
M
Honda
Hisashi
H
Yamazaki
Toshio
T
Hirota
Hiroshi
H
D007532:Isoleucine / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008968:Molecular Conformation; D010103:Oxygen Isotopes; D014633:Valine / Q000737:chemistry*
D010103:Oxygen Isotopes; D007532:Isoleucine; D014633:Valine