CYCLIC VOLTAMMETRY OF MITOMYCIN-C AND DNA

Cyclic voltammetry (CV) in connection with the hanging mercury drop electrode was used to study mitomycin C (MC) and its mixtures with DNA. CV of the MC solution (without DNA) revealed that (a) at low MC concentrations (around 10 mu M) the voltammetric cathodic peaks increase with consecutive cycles in the repeated cycle mode, (b) the CV responses of MC (both in the single-sweep and repeated cycle modes) depend strongly on the potential E(A) co which MC is adsorbed at the electrode, (c) if the adsorption is performed at E(A) corresponding to the potentials of MC reduction, MC is so strongly bound to the electrode that the MC layer can be transferred to the electrolyte (not containing any dissolved MC) where it produces a response not substantially different from that obtained with the electrode immersed in the MC solution. These results have been tentatively explained by the reduction-initiated polymerization and/or insolubilization of MC at the electrode. Easy preparation of the MC-modified electrode demonstrated in this paper may find practical applications, namely in MC analysis. Preliminary results are reported on the behaviour of MC + DNA mixtures. The addition of double-stranded or single-stranded (denatured) DNAs into the MC solution results in suppression of the MC CV peaks in the first cycle. In the second cycle a new reversible couple appears which increases with the number of cycles. The anodic peak G of DNA (due to guanine) decreases simultaneously. These preliminary results suggest that some potential-controlled interactions of MC with DNA might occur at the electrode.