Influence of DNA on melatonin’s actions. (a) Detection of melatonin induced Cu(I) production in the presence of DNA. Reaction mixture contained 0.3 mM BCS, 50 μM Cu(II), 1 mM melatonin (MT), and indicated concentrations of DNA in 0.05 M PBS (pH 7.4), and was incubated at 37 °C for 30 min. (b) ROS levels. 1 μg/mL (DNA concentration) = 3 μM DNA phosphates (P). [Cu]/[P] is the ratio of the molar concentration of metal ions and DNA phosphates. Chemicals as indicated were mixed in 0.05 M PBS (pH 7.4). Data are presented as the mean of two replicates; the error bar represents the range. In most data points, the range was smaller than the symbol.