Macromolecular nature of nucleic acids in metal interactions

Abstract

The conformational changes of nucleic acid macromolecules as a result of rotation around CC, CO, CN covalent bonds occur without destruction of the chains, but they can lead to the loss of biological function; this can be seen in interactions with metal ions of nucleic acids. The latter are ambidentate ligands and supply by complex formation different sites of binding, sometimes cooperatively, in polyfunctional chains. This leads to the formation in nucleic acid macromolecules of different coordination centers, among them the unsaturated, deformed type: pure phosphate, mixed phosphate-base, pure base, crosslinked base, sandwich, complementary paired base and others. The probability of the centers is discussed. As a result of complex formation with nucleic acid macromolecules there are mutual influences between fuctional groups of the chain, those of electronic origin, conjugations, fields effects, dispersion interactions, hydrogen bonding, solvation, supermolecular structure formation and so on. The interactions mentioned can not so far be expressed in quantitative ways nor can their contributions to equilibrium constants of macromolecular complex formation be written explicitly, therefore the way of describing polymeric complexing systems is through the use of averaged values. Various examples of the interactions of metal ions with macromolecular chains of DNA and RNA, pH-dependence, conformational changeability and reversibility, as well as the possibility of modelling the macromolecules under study are given.