Determination of protein-ligand binding affinity by NMR: observations from serum albumin model systems

The usefulness of bovine serum albumin (BSA) as a model protein for testing NNIR methods for the study of protein-ligand interactions is discussed. Isothermal titration calorimetry established the binding affinity and stoichiometry of the specific binding site for L-tryptophan, D-tryptophan, naproxen, ibuprofen, salicylic acid and warfarin. The binding affinities of the same ligands determined by NNIR methods are universally weaker (larger KID). This is because the NNIR methods are susceptible to interference from additional non-specific binding. The L-tryptophan-BSA and naproxen-BSA systems were the best behaved model systems. Copyright (c) 2005 John Wiley & Sons, Ltd.