Figure 1.

Schematic illustration of the sensitivity gained when using the presented methodology. The arbitrary chemical shift of a protein nucleus, shown in the 1D NMR trace (in gray), is altered when in fast equilibrium with either a native or diamagnetically tagged ligand (dark gray, δ_M), or with a paramagnetically tagged ligand (red, δ_PCS). For weak affinity ligands, the protein nucleus chemical shift change caused by a diamagnetic ligand (δ_M) may be very small, whereas the pseudocontact shift induced by a paramagnetic ligand (δ_PCS) is reliably measurable.