Copper(I)-bleomycin. A structurally unique oxidation-reduction active complex

Cu(I) and Cu(II) form stable 1:1 complexes with bleomycin (BLM). The affinity of both metals for the drug is greater than that of Fe(II). Cu(I)-BLM A₂ binds to calf thymus DNA with about the same affinity as Fe(II)-BLM, as judged by DNA-induced fluorescence quenching of the bithiazole moiety of BLM. Based on ¹H NMR and potentiometric titration data, the Cu(I) complexes of BLM are shown to have geometries very different than those of other BLM-metal(II) complexes studied thus far. As Cu(I)-BLM is oxidation-reduction active, its geometry is of importance in defining the structural requirements for BLM activity.