college of Chemistry and Molecular Engineering, Qingdao University of Science and Technology. Qingdao 266042, P.R. China E-mail : zhangshush@public.ad.sd.cn Department of Chemistry, East China Normal University, Shanghai 200062, P. R. China Manuscript received 24 June 2004, accepted 12 January 2005 ([CuL(C6H5N2O2) (CIO4)2.H2O, CuL) (L = N-(5-sulfosalicylidene)-4'-nitraniline) can strongly bind to DNA. The interaction between CuL and salmon sperm DNA in 0.1 mol L-1 NaOAc-HOAc (pH 4.8) has been investigated by Cyclic voltammetry and UV/Vis spectroscopy. The observed oxidative peak for the central copper ion of CuL from cyclic voltammogram is shown at the glassy carbon electrode. It has been found that the oxidative peak current decreased significantly with increasing concentrations of DNA. In addition, the absorbance of CuL at its absorption peaks also decreased in the presence of DNA. All experimental results indicate that CuL can hind to DNA to form a 1 : 1 association complex with the binding constant of 1.05 x 105 L mol-1, and the major binding mode of CuL to DNA is "electrostatic binding".