Orientational information from TEDOR spectral sidebands

In a dipolar-coupled spin-1/2 network of the type (15)N1-C-13-(15)N2, an assessment of the sensitivity of the N --> C and C --> N TEDOR sideband intensities to the Euler angles defining the orientation of the two heteronuclear dipolar vectors in the C-13 and N-15 chemical shift (CS) tenser principal axes system has been carried out via numerical calculations. The results clearly indicate the potential of TEDOR MAS NMR spectroscopy for the characterization of the CS tenser orientation in the molecular frame. The efficacy of the method has been experimentally illustrated by TEDOR studies on a polycrystalline sample of [1, 3 - N-15(2), 2 - C-13]uracil, which is one of the four bases in RNA. (C) 2001 Academic Press.