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Inter-Dna Attraction Mediated By Divalent Counterions, Xiangyun Qiu, Kurt Andresen, Lisa W. Kwok, Jessica S. Lamb, Hye Yoon Park, Lois Pollack
Inter-Dna Attraction Mediated By Divalent Counterions, Xiangyun Qiu, Kurt Andresen, Lisa W. Kwok, Jessica S. Lamb, Hye Yoon Park, Lois Pollack
Physics and Astronomy Faculty Publications
Can nonspecifically bound divalent counterions induce attraction between DNA strands? Here, we present experimental evidence demonstrating attraction between short DNA strands mediated by Mg2 ions. Solution small angle x-ray scattering data collected as a function of DNA concentration enable model independent extraction of the second virial coefficient. As the [Mg2] increases, this coefficient turns from positive to negative reflecting the transition from repulsive to attractive inter-DNA interaction. This surprising observation is corroborated by independent light scattering experiments. The dependence of the observed attraction on experimental parameters including DNA length provides valuable clues to its origin.
Measuring Inter-Dna Potentials In Solution, Xiangyun Qiu, Lisa W. Kwok, Hye Yoon Park, Jessica S. Lamb, Kurt Andresen, Lois Pollack
Measuring Inter-Dna Potentials In Solution, Xiangyun Qiu, Lisa W. Kwok, Hye Yoon Park, Jessica S. Lamb, Kurt Andresen, Lois Pollack
Physics and Astronomy Faculty Publications
Interactions between short strands of DNA can be tuned from repulsive to attractive by varying solution conditions and have been quantified using small angle x-ray scattering techniques. The effective DNA interaction charge was extracted by fitting the scattering profiles with the generalized one-component method and inter-DNA Yukawa pair potentials. A significant charge is measured at low to moderate monovalent counterion concentrations, resulting in strong inter-DNA repulsion. The charge and repulsion diminish rapidly upon the addition of divalent counterions. An intriguing short range attraction is observed at surprisingly low divalent cation concentrations, ~16 mM Mg2+. Quantitative measurements of inter- DNA potentials …