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 cuiigga (gga = glycylglycyl-l-alanine), cuiig3 (g3 = triglycine) or cuiig4 (g4 = tetraglycine) and ni(ii) traces, causes rapid formation of the respective cu(iii) complex, with simultaneous o2 uptake and s(iv) oxidation. so3？- and ho？ 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 cuibca complex formation, there is the possible formation of carbon centered radical of bca or peroxyl radical (roo？) capable of oxidizing dna bases. the intensity of dna damage in the presence of these cu(ii) complexes and s(iv) (10-300 μmol l-1) followed the order: cuiibca ～ cuiig4 ～ cu(ii) (added as cu(no3)2) > cuiig3 ～ cuiigga. specifically for cuiibca the damage occurred even at lower s(iv) concentration (0.1 μmol l-1). for the cu(ii) complexes with glycylglycylhistidine, glycylhistidylglycine, glycylhistidyllysine and glycylglycyltyrosylarginine the cu(iii) formation and the dna damage was not observed.