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Effects of calcium and manganese ions on the helix–coil transition of DNA

1983; Wiley; Volume: 22; Issue: 7 Linguagem: Inglês

10.1002/bip.360220704

1097-0282

Yu. P. Blagoı̆, V. A. Sorokin, Vladimir A. Valeev, Galina O. Gladchenko,

Electrostatics and Colloid Interactions

Abstract The thermal denaturation method was employed to study the effect of Ca 2+ and Mn 2+ ions on the DNA helix–coil transition parameters at Na + concentrations of 10 −3 –10 −1 M . At low ion concentrations, thermal stability increases, the melting range passes through a maximum, and the denaturation curves become asymmetric. These changes are quantitatively similar for Mn 2+ and Ca 2+ ions. With a further increase in the concentration of bivalent ions, the conformational transition temperatures pass through a maximum, and the melting range first tends to saturation and then rapidly decreases to 1–2°C. The Mn 2+ concentrations, at which the above effects occur, are an order of magnitude lower than the Ca 2+ concentrations. Comparison of experimental results and calculation in terms of the ligand theory permitted estimation of binding constants characterizing association between Mn 2+ and Ca 2+ ions and bases of native and denatured DNA. We show that, unlike the interaction with phosphates, bivalent ion–DNA base binding is weakly dependent on monovalent ion concentration in the solution.