2.2.2. SMARTS string SMARTS (SMILES Arbitrary Target Specification) is an extension of SMILES useful for performing a search by substructure to find structural fragments paired with other matching substructures . SMARTS has applications in studies based on the search for structural fragments in chemical libraries, such as virtual screening and molecular docking studies. In addition, SMARTS notation has been used to determine Pan Assay Interference Compounds (PAINS) in chemical libraries for high throughput screening . Figure shows SMILES and SMART representations of a natural product (benzopyranone) present in chemical libraries. SMILES and SMART notation of the 3-phenyl-benzopyran-4-one core using different structure editors. Here it is observed that the representation of SMILES presents a different ordering of the characters in its linear notation, while the SMART better defines the structure, avoiding errors when using different structural editors. This difference is explained by the fact that in structural editors, for example, aromatic rings are represented in upper case (when they should be lower case), and this occurs because aromaticity has not been considered, and benzene is considered as tricyclohexene.