Influence of Cu(II) on the interaction of sulfite with DNA

The quantitative influence of Cu(II) on the interaction of eukaryotic DNA with sulfite (SO32−), which is a derivative of sulfur dioxide in the human body, was studied using ultraviolet (UV) absorption spectrometry. The results showed that under physiological pH conditions, SO32− reacted weakly with DNA at concentrations of up to 10−1 M, at which point a rapid increase in the reaction constant and the reaction number of SO32− with DNA was observed. The addition of Cu(II) at concentrations ranging from 6.67 × 10−4 to 3.33 × 10−3 M to DNA-SO32− binary systems increased the reaction constant of SO32− with DNA 41- to 115-fold at a low concentration of SO32− (10−3 M), and 4- to 84-fold at an intermediate concentration of SO32− (10−2 M), but had little influence on the reaction number of SO32− with DNA compared with the absence of Cu(II). When the concentration of SO32− reached 10−1 M, the presence of Cu(II) reduced the reaction number but had no effect on the reaction constant of SO32− with DNA. These results show that the efficiency of SO32− is increased in the presence of Cu(II) at high concentrations of SO32−.