Reaction of platinum cytostatics of the second generation with deoxyribonucleic acid

Adducts of native calf thymus DNA with several platinum compounds with or without antitumour activity were prepared and their chiroptical and renaturation properties investigated. It was found that at high levels of binding cis-dichlorodiammineplatinum(II) and all other substances with antitumour activity induced changes in circular dichroic spectra of DNA which were attributed to formation of "premelted" regions in the double-stranded DNA. On the other hand, the substances with no antitumour effect induced changes corresponding to formation of single-stranded regions in DNA molecules, even at low levels of binding.