TOTO is a molecular 2D-descriptor introduced by NILAKANTAN (Nilakantan R., J. Chem. I n j Comput. Sci. 1987, 27, 82-85) used to encode molecular topology.

TOTO is based on fragments of molecular connectivity (topological torsions) and associated atomic properties.

TOTO is used for very fast 2D similarity searches of large compound spaces, when the 2D and/or 3D structrure of already validated ligands is available.