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.
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Qiu, X., Andresen, K., Kwok, L.W., Lamb, J.S., Park, H.Y., & Pollack, L. (2007). Inter-DNA attraction mediated by divalent counterions. Physical Review Letters,99(038104). http://dx.doi.org/10.1103/PhysRevLett.99.038104
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© 2007 The American Physical Society