Magnitudes and orientations of the N-15 chemical shift tensor of [1-N-15]-2 '-deoxyguanosine determined on a polycrystalline sample by two-dimensional solid-state NMR spectroscopy

The magnitudes and orientations of the N-15 chemical shift tensor of [1-N-1 5]-2'-deoxyguanosine were determined from a polycrystalline sample using th e two-dimensional PISEMA experiment. The magnitudes of the principal values of the N-15 chemical shift tensor of the N1 nitrogen of [1-N-15]-2'-deoxyg uanosine were found to be sigma(11) = 54 ppm, sigma(22) = 148 ppm, and sigm a(33) = 201 ppm with respect to ((NH4)-N-15)(2)SO4 in aqueous solution. Com parisons of experimental and simulated two-dimensional powder pattern spect ra show that sigma(33N) approximately collinear with the N-H bond. The tens or orientation of sigma(33N) for N1 of [1-N-15]-2'-deoxyguanosine is simila r to the values obtained for the side chain residues of N-15(epsilon 1)-try ptophan and N-15(pi)-histidine even though the magnitudes differ significan tly. (C) 1999 Academic Press.