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Mechanism of DNA Strand Cleavage Induced by Hexaaza Macrocyclic Nickel (II) Complex

The hexaaza macrocyclic nickel(II) complex (Ni(II)L—1,8-Dihydroxyethyl-1,3,6,8,10,13-hexaazacyclotetradecane nickle(II) perchlorate monohydrate) was synthesized and purified. The electrochemical character of Ni(II)L was measured, and the interaction of Ni(II)L with calf thymus DNA (CT-DNA) was studied using electrochemical techniques, emission and viscometry, and circular dichroic spectral measurements. All of the experiments suggested that the complex interacted with DNA primarily by partial intercalation. The cyclic voltammetry (CV) showed that the currents of both the reduction peak and the oxidation peak decreased significantly in the presence of DNA, which indicated that Ni(II)L could interact with DNA. The fluorescence intensity of the DNA-ethidium bromide(EB) system decreased distinctly when Ni(II)L was added. The results indicated that Ni(II)L may be completed effectively with EB for the intercalative binding sites. The viscosity of DNA would be decreased slightly by the addition of the complex. Circular dichroic spectral studies revealed that B conformation of CT-DNA became more A-like in structure on interaction with the complex. Noticeably, the complex has been found to cleave plasmid pBR 322 by agarose gel electrophoresis and cleave CT-DNA by high-performance liquid chromatography (HPLC).