The WaterLOGSY NMR experiment is a powerful tool for the studies of protein/RNA/DNA–small molecule interactions. WaterLOGSY involves the transfer of magnetization between water molecules, receptors (protein/RNA/DNA), and small molecules via chemical exchange and the NOE effect. This is a reliable method to identify small molecules that bind with a binding affinity (KD) in the μM to mM region. Additionally, this experiment allows for the determination of the KD via ligand titration. This experiment requires optimization of the experimental setup and thus requires either NMR staff to run or robust training. Finally, ligand binding orientation by identification of the water-accessible ligand protons.
Opposite signs for signals from free versus receptor-bound ligands are observed enabling one to easily discriminate binders and non-binders:
