iso-ADP ribose (isoADPr) is a ligand used for protein nucleic acid modification. iso-ADP ribose is a structure comprising parts of two consecutive ADP-ribosyl units within the PAR chain. iso-ADP ribose is the small-molecule ligand for RING finger protein 146 (RNF146) WWE. A single iso-ADP ribose molecule triggers the activation of RNF146 by interacting with the basic Lys61 residue in the RING domain.