HR relaxometry can also allow for easily identifying weak interactions between ligands and macromolecules. The detection of the relaxation profiles of ligand nuclei permits to observe the occurrence of binding from the field dependence of their relaxation rates. In the absence of binding the rates are expected to be basically field independent, as a result of the short reorientation time of the ligand molecule, whereas in the presence of binding the reorientation time becomes that of the macromolecule, so that a dispersion in the relaxation profile must appear.