The Interaction of Heavy Metal Ions with DNA

Abstract

The effect of metal ions upon conformation of DNA was realized early, when it became apparent that metal ions are involved in the stabilization of the Watson-Crick double helix^1,2. Metal ions react with a variety of electron-donor sites on polynucleotides³. There are two main sites of interaction, the phosphate moieties of the ribose-phosphate backbone and the electron donor groups of the bases. The two types of interaction carry with them quite different effects upon the structure of polynucleotides. Reactions with the phosphate means stabilization of ordered structures but cleavage of phosphodiester bonds at high temperature. Whether the binding is non-specific, i.e., totally predictable on the basis of electrolyte theory, or whether specific bonds to the phosphate are produced, the result is to neutralize the array of negative charges on the double helix and thus to stabilize it. Such stabilization is accompanied by an increase in the “melting temperature” of DNA⁴.