Principles of Dipolar Coupling Anisotropic media NMR experiments Types of RDC's Applications The dipolar coupling between two atoms A and B, DAB, is related to the internuclear distance, <rAB-3>, and to the angle between the vector connecting the interacting nuclei and the applied magnetic field (K), <3cos2K-1>, where the brackets indicate average sampling. These couplings can be a valuable source of distance and angular structural data for NMR studies of macromolecules because direct information on the orientations of the corresponding bond vectors relative to the protein's magnetic susceptibility tensor is provided. However, molecular tumbling averages these interactions to zero in conventional isotropic solutions. It has been shown that residual dipolar couplings (RDC's) can be measured by utilizing some type of anisotropic media. that allows partial alignment and, therefore, non-vanishing dipole-dipole interactions. Such incomplete directional averaging of macromolecules in liquid crystalline media allows routine measurement of residual dipolar couplings while retaining conditions essential for high/resolution solution-state NMR.
General Reading: 02ENC411 , 03CONC10 and 04CONC22 RDCs in biomolecules: 01COP532 , 02JB1-22 , 01PROG175 , B03GLY231 , B03ZER179 , 01METH127 , 01COP584 , 01CONC238 , 03PROT1 , 04CR3519 , 04PROG189-44 and 05METH175