Yamada Kazuhiko, Nemoto Takahiro, Asanuma Miwako, Honda Hisashi, Yamazaki Toshio, Hirota Hiroshi
RIKEN Genomic Sciences Center, 1-7-22 Suehiro, Tsurumi, Yokohama 230-0045, Japan.
Solid State Nucl Magn Reson. 2006 Oct;30(3-4):182-91. doi: 10.1016/j.ssnmr.2006.09.003. Epub 2006 Sep 30.
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.
我们对L-缬氨酸和L-异亮氨酸中四个不同位点的羧基氧核磁共振参数进行了实验研究。通过分析二维（17）O多量子魔角旋转（MQMAS）和/或一维MAS光谱，获得了这些化合物的羧基（17）O四极耦合常数C（Q）和各向同性化学位移δ（iso）。发现C（Q）和δ（iso）的值分别在7.00 - 7.85 MHz和264 - 314 ppm范围内。对一整簇L-缬氨酸分子和一些理论模型进行了密度泛函水平的广泛量子化学计算。计算结果表明，（17）O核磁共振参数与C - O键长之间存在相关性，这有助于光谱归属。结果还表明，L-缬氨酸的扭转角在确定（17）O核磁共振参数的大小方面起着重要作用。
