Hydrogen-bonding Effect on 15n Nmr Chemical Shifts of the Glycine Residue of Oligopeptides in the Solid State as Studied by High-resolution Solid-state Nmr Spectroscopy

19 HIgh-resolutIOn I5N NMR spectra of a vanety ofsohd ohgopeptIdes (X-Gly-Gly) contammg glycme resIdues have been measured, of whIch the crystal structures had already been determmed by X-ray dIffractIOn The expenmental '5N chemIcal shIfts of the glycme reSIdues were plotted agamst the N"'O hydrogen bond length and the N-H bond length m the :-C=O··· H-N; type hydrogen bond form, respectively It was found that the decrease of the N H bond length leads to a hnear mcrease m ION shIeldmg, but there IS no clear relatIOnshIp between the I5N chemIcal shIfts and the N· .. 0 separatIOn Further, I5N chemIcal shIft calculations were carned out usmg a model compound, by the FPT -INDO method, m order to further understand the nature of the hydrogen bond The calculated results reasonably explam the expenmental ones