The results of various 15 N solid-state NMR experiments perin the molecular principal axis system (PAS) is necessary formed on solid samples of doubly 15 N-labeled 3,5-dimethylpyrafor the analysis of several solid-state NMR experiments, e.g., zole, 5-methyl-3-phenylpyrazole, (PMP), and 3,5-diphenylp
15N Chemical Shift Tensor Magnitude and Orientation in the Molecular Frame of Uracil Determined via MAS NMR
✍ Scribed by Jörg Leppert; Bert Heise; Ramadurai Ramachandran
- Publisher
- Elsevier Science
- Year
- 2000
- Tongue
- English
- Weight
- 138 KB
- Volume
- 145
- Category
- Article
- ISSN
- 1090-7807
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✦ Synopsis
The potential of heteronuclear MAS NMR spectroscopy for the characterization of (15)N chemical shift (CS) tensors in multiply labeled systems has been illustrated, in one of the first studies of this type, by a measurement of the chemical shift tensor magnitude and orientation in the molecular frame for the two (15)N sites of uracil. Employing polycrystalline samples of (15)N(2) and 2-(13)C, (15)N(2)-labeled uracil, we have measured, via (15)N-(13)C REDOR and (15)N-(1)H dipolar-shift experiments, the polar and azimuthal angles (θ, psi) of orientation of the (15)N-(13)C and (15)N-(1)H dipolar vectors in the (15)N CS tensor frame. The (θ(NC), psi(NC)) angles are determined to be (92 +/- 10 degrees, 100 +/- 5 degrees ) and (132 +/- 3 degrees, 88 +/- 10 degrees ) for the N1 and N3 sites, respectively. Similarly, (θ(NH), psi(NH)) are found to be (15 +/- 5 degrees, -80 +/- 10 degrees ) and (15 +/- 5 degrees, 90 +/- 10 degrees ) for the N1 and N3 sites, respectively. These results obtained based only on MAS NMR measurements have been compared with the data reported in the literature.
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