Mechanisms of DNA cleavage by copper complexes of 3-clip-phen and of its conjugate with a distamycin analogue.

Mechanisms of DNA oxidation by copper complexes of 3-Clip-Phen and its conjugate with a distamycin analogue, in the presence of a reductant and air, were studied. Characterisation of the production of 5-methylenefuranone (5-MF) and furfural, associated with the release of nucleobases, indicated that these copper complexes oxidised the C1' and C5' positions of 2-deoxyribose, respectively, which are accessible from the DNA minor groove. Oxidation at C1' was the major degradation route. Digestion of DNA oxidation products by P1 nuclease and bacterial alkaline phosphatase allowed characterisation of glycolic acid residues, indicating that these copper complexes also induced C4' oxidation. However, this pathway was not associated with base propenal release. The ability of the copper complex of the 3-Clip-Phen conjugate with the distamycin analogue to produce sequence-selective DNA cleavage allowed confirmation of these mechanisms of DNA oxidation by PAGE. Comparison of DNA cleavage activity showed that conjugation of 3-Clip-Phen with a DNA minor groove binder, like the distamycin analogue, decreased both its ability to perform C1' oxidation as well as the initial rate of the reaction, but this conjugate is still active after 5 h at 37 degrees C, making it an efficient DNA cleaver.