Interactions between bleomycins and metals.

Gel filtration has shown that there are considerable differences between the metal complexes of bleomycin A2 and B2 with indium, cobalt or copper. Differences in the rates of formation of the complexes have also been found and it is thought that these effects are due to a difference in co-ordination between the metals and the bleomycin. The co-ordination changes are thought to be the cause of the differences in in vivo distribution of metal bleomycin complexes found in the radiodiagnosis of tumours. The ease of formation of the copper or cobalt complexes is suggested as a possible mechanism for the inhibition of the attack of DNA by bleomycins.