Measurement of Ligand–Target Residence Times by (1)H Relaxation Dispersion NMR Spectroscopy

[Image: see text] A ligand-observed (1)H NMR relaxation experiment is introduced for measuring the binding kinetics of low-molecular-weight compounds to their biomolecular targets. We show that this approach, which does not require any isotope labeling, is applicable to ligand–target systems involving proteins and nucleic acids of variable molecular size. The experiment is particularly useful for the systematic investigation of low affinity molecules with residence times in the micro- to millisecond time regime.