Paramagnetic Cross-Correlation Rate Restraint

These are restraints derived from cross-correlation between Curie and dipolar relaxation. The force constant can be weighted by the cube of the distance of the nuclear pair from the paramagnetic metal. The proportionality coefficient can be fitted in the same way as the tensor parameters from the pseudocontact shift and the paramagnetic residual dipolar couplings (Banci et al., 2004).