Residual Dipolar Couplings RDCs

Although RDCs were reported as early as 1963 by Englert and Saupe [23], their measurement and applicability for structural investigations has been limited to very small molecules with typically less than 10 protons until a few years ago. RDCs of a solute molecule can only be obtained if it is at least partially aligned with respect to the magnetic field in a so-called alignment medium. For conven- 

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NMR is the experimental tool of choice to explore conformational properties, especially of flexible small molecules in solution [55-57], Interpretation of NMR-derived structural parameters in combination with molecular modeling usually offers a view of the accessible conformations to ligands. The most relevant structural parameters derived from NMR are interproton distances obtained from NOE or ROE experiments, dihedral angle restraints from 3J scalar coupling measurements and, recently, residual dipolar couplings (RDCs) [58],... 

Abstract Residual dipolar couplings (RDCs) have already revolutionized biomolecular... 

Lanthanide ions with anisotropic molecular magnetic susceptibility tensor Ay, for example, Er , Tm , or Yb , allow valuable structural information to be extracted from pseudocontact shifts (PCS, see also Section 3.6) and residual dipolar couplings (RDCs) arising from the partial alignment of the -labeled biomolecules in the induced magnetic field (Su et al., 2008b) ... 

While methods of spectrum analysis capable of super-resolution exist, that is, methods that can achieve resolution greater than l/Wx, the most common of these, linear prediction (LP) extrapolation, has substantial drawbacks. LP extrapolation is used to extrapolate signals beyond the measured interval. While this can dramatically suppress truncation artifacts associated with zero-filling as well as improve resolution, because LP extrapolation implicitly assumes exponential decay it can lead to subtle frequency bias when the signal decay is not perfectly exponential [8]. This bias can have detrimental consequences for applications that require the determination of small fi-equency differences, such as measurement of residual dipolar couplings (RDCs). 

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