ChEMBL, an open-access database, contains more than 5 million interactions between proteins and ligands that have been published in peer-reviewed journals or reported by laboratories and screening centers . Under ChEMBL’s “Ligand Search” tab, you can enter a compound’s SMILES notation in the “List Search” box and click “Fetch Compounds.” On the next page, clicking on the ChEMBL compound identifier under the 2-D drawing takes you to the Compound Report Card page, which includes the “Protein Target Classes” and tables containing the proteins that are predicted to bind with the highest affinity (Nucleic Acids Res, 40:D1100-07,2012). Registration not required.