Abstract
The study of metal ion effects on the structure and conformational stability of DNA is an important problem of the nuclear acid physics connected with biological functions of DNA-macromolecules. As shown by a number of viscometric studies[1–3], the addition of bivalent metal ions at very small concentrations cause a considerable reduction of intrinsic viscosity of DNA [η]. In this paper we study the effect of Mn2+ and Cu2+ ions on DNA of high (~ 107) and low (~ 105) molecular weight in solutions of different ionic strength. Concentration dependences are calculated for the excluded volume parameter (ɛ), segment interaction parameter (Z) and expanding coefficient (α) for DNA macromolecules. These dependences permit one to judge upon the contributions of the electrostatic long- and short-range effects characterized by the values of ɛ and statistical segment A during the DNA interaction with metal ions. The effect of different degrees of ion binding (τ) upon DNA intrinsic viscosity is analysed in terms of the theory of equilibrium ion-DNA binding. This approach may prove efficient in estimating the ion-DNA constants from experimental results on viscosity.
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