ja0367041_si_001.pdf (111.25 kB)
Determination of the Glycosidic Bond Angle χ in RNA from Cross-Correlated Relaxation of CH Dipolar Coupling and N Chemical Shift Anisotropy
journal contribution
posted on 2004-02-25, 00:00 authored by Elke Duchardt, Christian Richter, Oliver Ohlenschläger, Matthias Görlach, Jens Wöhnert, Harald SchwalbeA new heteronuclear NMR pulse sequence, the quantitative Γ(HCN) experiment, for the
determination of the glycosidic torsion angle χ in 13C,15N-labeled oligonucleotides is described. The Γ(HCN)
experiment allows measurement of CH dipole−dipole, N chemical shift anisotropy cross-correlated relaxation
rates (
and
for pyrimidines and
and
for purines). A nucleotide-specific
parametrization for the dependence of these Γ-rates on χ based on 15N chemical shift tensors determined
by solid-state NMR experiments on mononucleosides (Stueber, D.; Grant, D. M. J. Am. Chem. Soc. 2002,
124, 10539−10551) is presented. For a 14-mer and a 30-mer RNA of known structures, it is found that the
Γ(HCN) experiment offers a very sensitive parameter for changes in the angle χ and allows restraining of
χ with an accuracy of around 10 degrees for residues which do not undergo conformational averaging.
Therefore, the Γ(HCN) experiment can be used for the determination of χ in addition to data derived from
3J(C,H)-coupling constants. As shown for the 30-mer RNA, the derived torsion angle information can be
incorporated as additional restraint, improving RNA structure calculations.