Fig. 1

Residual Dipolar Couplings in NMR Spectroscopy. a The behavior of a molecule with the magnetic field B₀ depends on physical properties. In its crystal form, the dipolar couplings are too larger, in an isotropic solution the dipolar interaction average to zero due to tumbling and no coupling is observed, whereas in an anisotropic solution with a partially oriented medium, small residual dipolar couplings are visible. b 2D ¹H-¹⁵ N HSQC spectra of a protein where each peak corresponds to the N–H resonance of an amino acid of the backbone. The spectra in green and red correspond to an isotropic solution decoupled in both ¹H and ¹⁵ N dimensions or only ¹⁵ N, respectively. The latter spectrum shows the same ¹⁵ N-¹H splitting for every amino acid peak and represents ¹⁵ N-¹H one-bond scalar coupling. The blue spectrum corresponds to the anisotropic solution decoupled in ¹⁵ N Dimension. The partial orientation allows observation of ¹⁵ N-¹H splitting and represents ¹⁵ N-¹H one-bond scalar coupling in addition to the residual dipolar coupling RDC, the total coupling