HYDROGEN-BONDING EFFECT ON N-15 NMR CHEMICAL-SHIFTS OF THE GLYCINE RESIDUE OF OLIGOPEPTIDES IN THE SOLID-STATE AS STUDIED BY HIGH-RESOLUTION SOLID-STATE NMR-SPECTROSCOPY

High-resolution 15N NMR spectra of a variety of solid oligopeptides (X-Gly-Gly) containing glycine residues have been measured, of which the crystal structures had already been determined by X-ray diffraction. The experimental 15N chemical shifts of the glycine residues were plotted against the N⋯O hydrogen bond length and the NH bond length in the {A figure is presented} type hydrogen bond form, respectively. It was found that the decrease of the NH bond length leads to a linear increase in 15N shielding, but there is no clear relationship between the 15N chemical shifts and the N⋯O separation. Further, 15N chemical shift calculations were carried out using a model compound, by the FPT-INDO method, in order to further understand the nature of the hydrogen bond. The calculated results reasonably explain the experimental ones. © 1990.