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

We have focused our interest on the tetrapyridoacridine ligand tetrapyrido[3,2-a:2′,3′-c:3′′,2″-h: 2triple prime,3triple prime-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.