Irreversibility of Conformational Changes and ZN2+Binding to DNA

Zinc is the second most abundant transition metal in the body. In biology, zinc is instrumental for signaling pathways that are used in the olfactory sensing pathway, among others. It is also present in the active sites of many enzymes, including the well-studied zinc finger protein motif. However, direct interactions of Zn2+ ions with DNA have been less extensively studied. We present measurements of Zn2+ ion binding to DNA by measuring conformational changes through circular dichroism and concordant measurements of the number of Zn2+ ions bound through inductively-coupled plasma atomic emission spectroscopy (ICP-AES). Furthermore, we monitor the zinc-induced changes in the conformation and binding in the presence of large excess of monovalent and divalent competing ions (Na+ and Mg2+). We find that the zinc-induced changes observed are largely irreversible when washing with these competing ions. These results are important in understanding how biological Zn2+ bound to DNA may act in the presence of competing ions in the body.