engleski

Effect of magnesium ions on the structure of DNA thin films

Interaction of the Mg+2 cations with DNA was previously studied by many authors as Mg ions show great affinity toward phosphate groups of DNA, thus neutralizing and stabilizing double helical structure [1-6]. However, due to great variety of experimental conditions, different authors report different affinities and preferable sites of Mg-DNA coordination, leaving particular mechanism of Mg-DNA interaction unclear. In order to address how the behavior of DNA evolves upon progressive addition of Mg2+ cations, utilizing Fourier transform infrared spectroscopy, we have investigated vibrational properties of dsDNA thin films in a broad range of added magnesium chloride salt concentration. Also, to eliminate/determine influence of intrinsic sodium and magnesium ions, we have investigated both Na-DNA and Mg-DNA thin films where Mg-DNA was obtained by extensive dialysis towards respective MgCl2 solutions. Our results demonstrate that going from the low to the high magnesium content, cation–DNA interaction changes in strength due to enhanced Debye screening, present in the both the backbone as well as the base regions [7]. Whereas lower Mg2+ salt concentrations stabilize the double-helix B conformation of dsDNA, extremely high non-physiological contents, larger than 150 mM, induce fundamental modifications of the secondary structure, which possibly indicate a transition into a more compact form.

DNA, DNA conformation, Interaction of the Mg+2 cations with DNA

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