Solid-state 17O NMR study of the electric-field-gradient and chemical shielding tensors in polycrystalline amino acids

✍ Scribed by Kazuhiko Yamada; Tadashi Shimizu; Masataka Tansho; Takahiro Nemoto; Miwako Asanuma; Mitsuru Yoshida; Toshio Yamazaki; Hiroshi Hirota

• Publisher: John Wiley and Sons
• Year: 2007
• Tongue: English
• Weight: 351 KB
• Volume: 45
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.2002

✦ Synopsis

Abstract

We have presented a systematic experimental investigation of carboxyl oxygen electric‐field‐gradient (EFG) and chemical shielding (CS) tensors in crystalline amino acids. Three ^17^O‐enriched amino acids were prepared: L‐aspartic acid, L‐threonine, and L‐tyrosine. Analysis of two‐dimensional ^17^O multiple‐quantum magic‐angle spinning (MQMAS), MAS, and stationary NMR spectra yields the ^17^O CS, EFG tensors and the relative orientations between the two tensors for the amino acids. The values of quadrupolar coupling constants (C~Q~) are found to be in the range of 6.70–7.60 MHz. The values of δ~iso~ lie in the range of 268–292 ppm, while those of the δ~11~ and δ~22~ components vary from 428 to 502 ppm, and from 303 to 338 ppm, respectively. There is a significant correlation between the magnitudes of δ~22~ components and CO bond lengths. Since CO bond length may be related to hydrogen‐bonding environments, solid‐state ^17^O NMR has significant potential to provide insights into important aspects of hydrogen bonds in biological systems. Copyright © 2007 John Wiley & Sons, Ltd.