The 13C and 15N chemical shift tensors of L-[1-13C]alanyl-L-[15N]alanine have been determined from the dipole-coupled powder patterns and verified with the decoupled spectra. The principal values of the 13C tensor are σ11 = -115.5, σ22 = -42.3, and σ33 = 33.5 ppm, and the polar angles relating the 13C-15N bond to the chemical shift tensor are β = 90° and α = -39.5°. Although the 13C powder pattern widths of AlaAla and AcGlyAlaNH2 differ by only 2%, the anisotropy and asymmetry parameters differ by 10 and 25%, respectively. The principal values for the 15N chemical shift tensor are σ11= 65.3, σ22 = 78.1, and σ33 = 215.5 ppm, and the orientation of the 13C-15N bond to the σ33 axis is 106°. AlaAla and AcGlyAlaNH2 show a striking difference in asymmetry parameters (0.06 vs. 0.16) and anisotropy (144 vs. 165).
|Original language||English (US)|
|Number of pages||4|
|Journal||Journal of the American Chemical Society|
|State||Published - 1987|
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