BindingDB 
 is a public, web-accessible database of measured binding affinities, focusing chiefly on the interactions of proteins considered to be candidate drug-targets with ligands that are small, drug-like molecules.  As of March, 2011, BindingDB contains about 650,000 binding data, for 5,700 protein targets and 280,000 small molecules.  BindingDB also includes a small collection of host–guest binding data of interest to chemists studying supramolecular systems.
The purpose of BindingDB is to support medicinal chemistry and drug discovery via literature awareness and development of structure-activity relations (SAR and QSAR); validation of computational chemistry and molecular modelling approaches such as docking, scoring and free energy methods; chemical biology and chemical genomics; and basic studies of the physical chemistry of molecular recognition.
The data collection derives from a variety of measurement techniques, including enzyme inhibition and kinetics, isothermal titration calorimetry, NMR, and radioligand and competition assays. BindingDB includes data extracted from the scientific literature by the BindingDB project, selected PubChem confirmatory BioAssays, and ChEMBL entries for which a well-defined protein target ("TARGET_TYPE=PROTEIN") is provided.