Fig. 4

Formation of 8-oxodG in calf thymus DNA by purpurin in the presence of Cu(II). (A) Reaction mixtures contained 100 μM/base calf thymus DNA, the indicated concentrations of purpurin and 20 μM CuCl₂ in 400 μl of 4 mM sodium phosphate buffer (pH 7.8) containing 5 μM DTPA. (B) Reaction mixtures contained 100 μM/base calf thymus DNA, 100 μM purpurin, 20 μM CuCl₂ and each scavenger or bathocuproine in 400 μl of 4 mM sodium phosphate buffer (pH 7.8) containing 5 μM DTPA. The concentrations of each scavenger and bathocuproine were as follows: 0.2 M ethanol, 0.1 M mannitol, 0.1 M sodium formate, 0.6 M methional, 50 U catalase, 50 μM bathocuproine. Reaction mixtures were incubated at 37 °C for 1 h under light shielding. After ethanol precipitation, the DNA was digested to nucleosides with nuclease P₁ and calf intestine phosphatase, then analyzed with an HPLC-ECD system. * p < 0.05 vs 0 μM. # p < 0.05 vs purpurin plus Cu(II). Significance was analyzed using Student t-test