The 15N chemical shift tensors of a homologous series of peptides of the form N-acetyl[1-13C]glycyl[15N]-X-amide (X = glycine, alanine, and tyrosine) and the unprotected dipeptide [1-13C]glycyl[15N]glycine hydrochloride have been determined from 13C dipole-coupled 15N powder patterns. It was found that the shift tensor principal values differ greatly while their molecular orientation does not. The common shift tensor orientation places σ22 perpendicular to the peptide plane, and σ33 at a 99° angle with respect to the C-N bond. The orientations of σ11 and σ22 were previously unknown for 15N chemical shift tensors of amides. Comparison of magic angle spinning (MAS) spectra with solution spectra shows significantly different solid and solution isotropic chemical shifts for several of the peptides studied, demonstrating that at least part of the variation in principal values is due to lattice effects. This conclusion is borne out by the MAS spectrum of N-acetyl[1-13C]glycl-[15N]phenylalaninamide, which shows at least three peaks corresponding to different lattice environments.
|Original language||English (US)|
|Number of pages||5|
|Journal||Journal of the American Chemical Society|
|State||Published - 1987|
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