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Phys Rev E Stat Nonlin Soft Matter Phys. 2013 Nov;88(5):052703. Epub 2013 Nov 5.

Effect of magnesium ions on dielectric relaxation in semidilute DNA aqueous solutions.

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  • 1Institut za fiziku, 10000 Zagreb, Croatia.
  • 2Department of Physics, University of Ljubljana and J. Stefan Institute, 1000 Ljubljana, Slovenia.


The effect of magnesium ion Mg(2+) on the dielectric relaxation of semidilute DNA aqueous solutions has been studied by means of dielectric spectroscopy in the 100 Hz-100 MHz frequency range. de Gennes-Pfeuty-Dobrynin semidilute solution correlation length is the pertinent fundamental length scale for sufficiently low concentration of added salt, describing the collective properties of Mg-DNA solutions. No relaxation fingerprint of the DNA denaturation bubbles, leading to exposed hydrophobic core scaling, was detected at low DNA concentrations, thus indicating an increased stability of the double-stranded conformation in Mg-DNA solutions as compared to the case of Na-DNA solutions. Some changes are detected in the behavior of the fundamental length scale pertaining to the single molecule DNA properties, reflecting modified electrostatic screening effects of the Odijk-Skolnick-Fixman type. All results consistently demonstrate that Mg(2+) ions interact with DNA in a similar way as Na(1+) ions do, their effect being mostly describable through an enhanced screening.

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