Figure 1.

Formation of the radical-derived DMPO adduct from the reaction of an equimolar mixture of all four DNA nucleosides with CuCl₂/H₂O₂ in the presence of DMPO. All components of the reaction must be present for the adduct formation. (A) The mixture contained 1 mM of all four DNA nucleosides, CuCl₂ (300 μM), H₂O₂ (100 μM) and DMPO (100 mM) and was incubated at 37°C for 1 h. Instrumental conditions: modulation amplitude, 1.0 G; time constant, 327 ms; receiver gain, 2 × 10⁴; and microwave power, 20 mW. (B) The EPR spectrum of the dAdo-DMPO radical derived from the reaction of adenosine with CuCl₂/H₂O₂ in the presence of DMPO. (C) The computer simulation of the dAdo-DMPO adduct.