Voltammetric studies of the interaction of pyrrolo[2,1-c][1,4]benzodiazepine (PBD) monomers and dimers with DNA

This study of the electrochemical activity of pyrrolo[2,1-c][1,4]benzodiazepine (PBD) molecules and their interaction with DNA extends previous similar studies on anthramycin by investigating a range of PBD monomers of various structures, and also the new PBD dimers which are shown here to be electroactive. A voltammetric study of seven pyrrolo[2,1-c][1,4]benzodiazepines, and the interaction of two examples of these with DNA in acetate buffer solution is described. Each of the PBDs studied was found to be electroactive in acidic medium, providing a well-defined cathodic peak between −0.8 and −0.9 V and an anodic peak, which sometimes appeared as a shoulder, between −0.6 and −0.8 V. It was found that the PBDs adsorbed onto the electrode and that the electrode process was quasi-reversible. In general, adding DNA to a solution of a PBD decreased the Ip value of the cathodic and anodic peaks, and shifted Ep negatively, consistent with decreasing concentrations of the PBD. No new peaks appeared and no significant change in the electrochemical parameters of the PBDs was observed, suggesting that the PBD-DNA complex may either be non-electroactive or have a decreased transport rate to the electrode (i.e., a low D value) This work has established that, in principle, the electrochemical methodology described here can be used to measure the kinetics of reaction of PBD molecules with DNA, and that the results are in accord with previously published studies using alternative techniques (e.g., UV spectroscopy). It is possible that the technique can be adapted in the future to measure the stoichiometry of PBD-DNA interaction.