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Updated: Jul 18, 2026

Structure and Coordination Determination of Peptide-metal Complexes Using 1D and 2D 1H NMR
Published on: December 16, 2013
Pseudo-CSA restraints for NMR refinement of nucleic acid structure
Alexander Grishaev1, Jinfa Ying, Ad Bax
1Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
Abstract:
Upon alignment of oligonucleotides in a magnetic field, the downfield TROSY component of the 13C-{1H} doublet changes its resonance frequency as a result of residual 13C-1H dipolar coupling (RDC) and residual 13C chemical shift anisotropy (RCSA), and the sum of these two second rank tensors is referred to as the pseudo-CSA. The experimentally measured difference in the resonance frequency of the 13C TROSY component in the aligned and isotropic samples is referred to as residual pseudo-CSA (RPCSA), and it can be used directly as a restraint during structure calculation. Because measurement of the RPCSA involves detection of the narrow TROSY 13C doublet component, it is applicable to systems with larger rotational correlation times than RDC measurement. The method is demonstrated for structure refinement of the helical region of a 24-nt stem-loop segment or ribosomal helix-35, uniformly enriched in 13C and 15N, with RPCSA values measured at 5 and 25 degrees C. Substantial cross-validated improvements in structural accuracy are obtained upon incorporation of RPCSA restraints.
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