Direct determination of a peptide torsional angle ψ by double-quantum solid-state NMR,

X. Feng, M. Edén, A. Brinkmann, H. Luthman, L. Eriksson, A. Gräslund, O. N. Antzutkin, and M. H. Levitt,
J. Am. Chem. Soc. 119, 2006-12007, (1997).
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We introduce a new solid-​state NMR method for directly estimating the molecular torsional angle of an isotopically-​labelled 15N-15C-13C-13N molecular fragment. The method is demonstrated on an isotopically-​labelled polycrystalline sample of gly-gly-gly.HCl. The value of ψ is determined to be 162°±5°, in good agreement with the X-ray structure.