Direct Determination of a Peptide Torsional Angle ψ by Double-Quantum Solid-State NMR,

A. Brinkmann, M. Edén, X. Feng, H. Luthman, L. Eriksson, A. Gräslund, O. N. Antzutkin, and M. H. Levitt,
39th Experimental NMR Conference, Asilomar, California, USA (Mar. 1998), poster.

We present a new solid-state NMR method for directly estimating the molecular torsional angle of an isotopically labelled 15N-13C-13C-15N molecular fragment [1]. The new method is a variety of the double-quantum heteronuclear field spectroscopy 2Q-HLF [2]. It exploits double-quantum coherences between neighboring 13C spins, excited under magic-angle-spinning conditions. The double-quantum coherences are allowed to evolve under the presence of the 15N-13C dipolar couplings, which are refocused by 180° pulses applied to the 15N [3]. This gives direct information about the local molecular geometry, i.e. without measuring distances. The method is demonstrated on an isotopically-labelled polycrystalline sample of gly-gly-gly.HCl. The absolute value of ψ is determined to be 162.5°, in good agreement with the X-ray structure.

  1. X. Feng, M. Edén, A. Brinkmann, H. Luthman, L. Eriksson, A. Gräslund, O. N. Antzutkin, and M. H. Levitt, Direct determination of a peptide torsional angle ψ by double-quantum solid-state NMR, J. Am. Chem. Soc. 119, 2006-12007, (1997). Abstract, Full text (PDF).
  2. X. Feng, Y. K. Lee, D. Sandström, M. Edén, H. Maisel, A. Sebald, and M. H. Levitt, Direct Determination of a Molecular Torsional Angle by Solid-State NMR, Chem. Phys. Lett. 257, 314-320, (1996).
  3. T. Gullion and J. Schaefer, Rotational-Echo Double-Resonance NMR, J. Mag. Res. 81, 196-200, (1989).
Dr. Andreas Brinkmann
NRC Metrology
National Research Council Canada
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