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.