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Updated: Jul 5, 2026

Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy
Published on: September 17, 2017
Protein backbone motions viewed by intraresidue and sequential HN-Halpha residual dipolar couplings
Beat Vögeli1, Lishan Yao, Ad Bax
1Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
Abstract:
Triple resonance E.COSY-based techniques were used to measure intra-residue and sequential H(N)-H(alpha) residual dipolar couplings (RDCs) for the third IgG-binding domain of protein G (GB3), aligned in Pf1 medium. Measurements closely correlate with values predicted on the basis of an NMR structure, previously determined on the basis of a large number of one-bond backbone RDCs measured in five alignment media. However, in particular the sequential H(N)-H(alpha) RDCs are smaller than predicted for a static structure, suggesting a degree of motion for these internuclear vectors that exceeds that of the backbone amide N-H vectors. Of all experimentally determined GB3 structures available, the best correlation between experimental (1)H-(1)H couplings is observed for a GB3 ensemble, previously derived to generate a realistic picture of the conformational space sampled by GB3 (Clore and Schwieters, J Mol Biol 355:879-886, 2006). However, for both NMR and X-ray-derived structures the (1)H-(1)H couplings are found to be systematically smaller than expected on the basis of alignment tensors derived from (15)N-(1)H amide RDCs, assuming librationally corrected N-H bond lengths of 1.041 A.
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