A variety of copper complexes with different structural features have been shown to bind double-helical DNA with binding constants of 10~4-10~7 M~(-1) and to promote double-strand DNA damage upon reductant/H_2O_2 activation. The interaction of the Cu complex with DNA results in hyperchromism and shifts to longer wavelengths of the strongest transitions in the Cu complexes, as well as striking hypochromism or hyperchromism of DNA absorption at 260nm. In the presence of DMPO as the spin trap, the solution of each copper complex exhibits typical four-line ESR spectra of the hydroxyl radical by ad...