Interaction with Transition Biometals

The binding between DNA and the alkaline-earth ions is electrostatic in nature, and occurs between the M cations and the phosphodiester groups of DNA. The increase in positive charge due to protoniza-tion of the bases decreases the DNA afSnity for the divalent alkaline-earth cations. 

Native DNA binds relatively strong to the alkaline-earth M because they stabilize the macromolecule. Experiments have confirmed that Mg binds more strongly to native DNA than to denatured DNA (Park and Kohel 1993, Sigel and Sigel 1996). 

The melting temperature (T ,), which is defined as the average temperature of transition, increases. 

Differences between the interaction of DNA with alkaline-earth and transition divalent metal ions result from investigations made on the binding constants (K ) using polarography, atomic absorption spectroscopy, and sedimentation analysis. For the alkaline-earth metals, K is decreased, and this is confirmed by the lower coordination tendency compared to that of the nucleo-bases. 

The electrostatic nature of the binding between the DNA polyanion and the various cations is explained by the existence of a diffuse electrostatic change-effect, which induces the formation of the DNA-M adducts. 

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This chapter deals with the interactions between DNA and divalent metal ions present in the organism ( biometals ) as bioconstituents or biochemical effectors (activa-tors/inhibitors) such as alkaline-earth metals (e.g., Ca, Mg) and the biologically active transition metals (e.g., Zn, Fe, Mn,... 

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