MITOMYCIN-C BINDING TO POLY[D(G-M(5)C)]

Poly[d(G-m(5)C)] was modified by reductively activated mitomycin C, an anti-tumour drug, under buffer conditions which are known to favour either the B or the Z conformations of DNA. C.d. and P-31-n.m.r. were used to characterize the poly[d(G-m(5)C)]-mitomycin cross-linked complexes, as well as the effects on the equilibrium between the B and Z forms of the polynucleotide. Mitomycin C appears to inhibit the B --> Z transition, even in the presence of 3 mM MgCl2, while the Z-form of poly[d(G-m(5)C)] does not interact significantly with the drug under bifunctionally activating conditions; thus no reversion from the Z-form to the B-form of the polynucleotide can be observed under the salt conditions which are required for the Z-form to exist.