Copper-mediated DNA photocleavage by a tetrapyridoacridine (tpac) ligand.

Abstract We have focused our interest on the tetrapyridoacridine ligand tetrapyrido[3,2- a :2′,3′- c :3′′,2″- h : 2‴,3‴- j ]acridine (tpac), as a model system for the preparation of novel copper-based artificial nucleases. The complex of copper(II)–tpac cleaves supercoiled pUC18 plasmid DNA in an oxidative manner by photoactivation with visible light, exhibiting maximum cleaving efficiency at 1:2 metal–ligand stoichiometric ratio. We propose an interaction of the copper–tpac complex with DNA through both major and minor grooves and a photocleavage mechanism via the formation of hydroxyl radicals and singlet oxygen or singlet oxygen-like species.