The influence of Cu(II), Mg(II) on the binding of adriamycin with DNA and the study on their interaction mechanism

Cu(II) and Mg(II) have different binding capacity with daunomycin, and have different combination mode with DNA. Selecting these two different metal ions, the influence of them on the binding constant of adriamycin with DNA and the related mechanism has been studied by using absorption and fluorescence spectroscopy. The result showed that Mg(II) has weaker binding capacity with the drug comparing Cu(II), but both Mg(II) and Cu(II) can obviously reduce the binding constant of DNA with the drug. Addition of Cu(II) to the drug–DNA binary system can cause the reduction of fluorescence in the system, but addition of Mg(II) to it can cause the enhancement of fluorescence in some conditions. This show that the influence of Cu(II) and Mg(II) on the binding of the drug with DNA may be by a different mechanism. According to the main function of Mg(II) to bind with the phosphate groups on DNA, it can be deduced that for the interaction of the aglycon portion of the drug into the base pairs of DNA, the electrostatic binding between amine group of the drug with the phosphate group on DNA is a prerequisite.