Synthesis, Structure, and Chemical Nuclease Activity of DNA with [Cu(dpq)(L–Met)Cl] · H2O

Abstract

A new mononuclear copper complex [Cu(dpq)(L–Met)Cl] ⋅ H₂O has been designed and synthesized using the phenanthroline derivative dipyridoquinoxaline (dpq). This complex has been characterized by element analysis and X-ray single crystal diffraction. The crystal structure of the complex belongs to a monoclinic system with space group C2/c. Binding of the complex to DNA has been investigated by absorption spectroscopy, fluorescence spectroscopy, and agarose gel electrophoresis. Spectrophotometric studies have showed that the mode of binding is intercalation with a binding constant K_b of 1.25 × 10³ L mol^–1. Additionally, the complex could quench an ethidium bromide-DNA complex. The apparent binding constant value for the complex is 1.89 × 10 ⁵ L mol^–1, which is slightly lower than the classical binding constant of 10⁷ L mol^–1. In addition, the quenching mechanism of the complex has been not static or dynamic. Agarose gel electrophoresis has shown that the complex cleaved circular pBR322 plasmid DNA to both nicked and linear forms; at higher concentrations and longer reaction times, the cutting results have been improved. The cleavage mechanism between the complex and plasmid DNA may involve singlet oxygen and hydroxyl radical as reactive oxygen species.