One- and two-dimensional 13C– 1H/ 15N– 1H dipolar correlation experiments under fast magic-angle spinning for determining the peptide dihedral angle φ

Abstract

A recently proposed 13C– 1H recoupling sequence operative under fast magic-angle spinning (MAS) [K. Takegoshi, T. Terao, Solid State Nucl. Magn. Reson. 13 (1999) 203–212.] is applied to observe 13C– 1H and 15N– 1H dipolar powder patterns in the 1H– 15N– 13C– 1H system of a peptide bond. Both patterns are correlated by 15N-to- 13C cross polarization to observe one- or two-dimensional (1D or 2D) correlation spectra, which can be simulated by using a simple analytical expression to determine the H–N–C–H dihedral angle. The 1D and 2D experiments were applied to N-acetyl[1,2- 13C, 15N] dl-valine, and the peptide φ angle was determined with high precision by the 2D experiment to be ±155.0°±1.2°. The positive one is in good agreement with the X-ray value of 154°±5°. The 1D experiment provided the value of φ=±156.0°±0.8°.