Oxidative DNA Damage Induced by S(IV) in the Presence of Cu(II) and Cu(I) Complexes

The DNA damage induced by S(IV) in the presence of some Cu(II) complexes in air saturated solution was investigated. The addition of S(IV) to an air saturated solution containing Cu(II)GGA (GGA = glycylglycyl-L-alanine), Cu(II)G(3) (G(3) = triglycine) or Cu(II)G(4) (G(4) = tetraglycine) and Ni(II) traces, causes rapid formation of the respective Cu(III) complex, with simultaneous O-2 uptake and S(IV) oxidation. SO3 center dot- and HO center dot were detected by EPR-spin trapping experiments. The DNA strand breaks were attributed to the oxysulfur radicals formed. In the reduction of Cu(II)/BCA (BCA = 4,4' dicarboxy-2-2'-biquinoline) by S(IV), with Cu(I)BCA complex formation, there is the possible formation of carbon centered radical of BCA or peroxyl radical (ROO center dot) capable of oxidizing DNA bases. The intensity of DNA damage in the presence of these Cu(II) complexes and S(IV) (10-300 mu mol L-1) followed the order: Cu(II)BCA similar to Cu(II)G4 similar to Cu(II) (added as Cu(NO3)(2)) > Cu(II)G(3) similar to CuIIGGA. Specifically for CuIIBCA the damage occurred even at lower S(IV) concentration (0.1 mu mol L-1). For the Cu(II) complexes with glycylglycylhistidine, glycylhistidylglycine, glycylhistidyllysine and glycylglycyltyrosylarginine the Cu(III) formation and the DNA damage was not observed.