STD NMR is a powerful and fast method used to study protein-ligand interactions, focusing on the signals of the ligand. Besides, values including KD, the association and dissociation kinetics (Koff and Kon respectively) can be obtained from STD NMR study as well. In the context that in drug discovery, ligand-based NMR screening and the bound conformation of a ligand through NMR are important tools, now the technique of saturation transfer difference NMR (STD-NMR) has been widely used to characterize ligand-receptor complexes for many years.