Yamada Kazuhiko, Shimizu Tadashi, Tansho Masataka, Nemoto Takahiro, Asanuma Miwako, Yoshida Mitsuru, Yamazaki Toshio, Hirota Hiroshi
RIKEN Genomic Sciences Center, 1-7-22 Suehiro, Tsurumi, Yokohama, 230-0045 Japan.
Magn Reson Chem. 2007 Jul;45(7):547-56. doi: 10.1002/mrc.2002.
We have presented a systematic experimental investigation of carboxyl oxygen electric-field-gradient (EFG) and chemical shielding (CS) tensors in crystalline amino acids. Three 17O-enriched amino acids were prepared: L-aspartic acid, L-threonine, and L-tyrosine. Analysis of two-dimensional 17O multiple-quantum magic-angle spinning (MQMAS), MAS, and stationary NMR spectra yields the 17O CS, EFG tensors and the relative orientations between the two tensors for the amino acids. The values of quadrupolar coupling constants (CQ) are found to be in the range of 6.70-7.60 MHz. The values of deltaiso lie in the range of 268-292 ppm, while those of the delta11 and delta22 components vary from 428 to 502 ppm, and from 303 to 338 ppm, respectively. There is a significant correlation between the magnitudes of delta22 components and C--O bond lengths. Since C--O bond length may be related to hydrogen-bonding environments, solid-state 17O NMR has significant potential to provide insights into important aspects of hydrogen bonds in biological systems.
我们对结晶氨基酸中的羧基氧电场梯度（EFG）和化学屏蔽（CS）张量进行了系统的实验研究。制备了三种富含(^{17}O)的氨基酸：L-天冬氨酸、L-苏氨酸和L-酪氨酸。对二维(^{17}O)多量子魔角旋转（MQMAS）、MAS和静态核磁共振谱进行分析，得出了氨基酸的(^{17}O) CS、EFG张量以及两个张量之间的相对取向。发现四极耦合常数（(C_Q)）的值在6.70 - 7.60 MHz范围内。(\delta_{iso})的值在268 - 292 ppm范围内，而(\delta_{11})和(\delta_{22})分量的值分别在428至502 ppm和303至338 ppm之间变化。(\delta_{22})分量的大小与C - O键长之间存在显著相关性。由于C - O键长可能与氢键环境有关，固态(^{17}O)核磁共振在深入了解生物系统中氢键的重要方面具有巨大潜力。
