Protein-Small Molecule Interactions by WaterLOGSY

WaterLOGSY is a ligand-observed NMR method that is widely used for the studies of protein-small molecule interactions. The basis of waterLOGSY relies on the transfer of magnetization between water molecules, proteins, and small molecules via the nuclear Overhauser effect and chemical exchange. WaterLOGSY is used extensively for the screening of protein ligands, as it is a robust, relatively high-throughput, and reliable method to identify small molecules that bind proteins with a binding affinity (K_D) in the μM to mM region. WaterLOGSY also enables the determination of K_D via ligand titration, although careful optimization of the experimental setup is required to avoid overestimation of binding constants. Finally, waterLOGSY allows the water-accessible ligand protons of protein-bound ligands to be identified, thus providing structural information of the ligand binding orientation. In this chapter, we introduce and describe the waterLOGSY method, and provide a practical guide for ligand screening and K_D determination. The use of waterLOGSY to study water accessibility is also discussed.