Measuring Inter-DNA Potentials in Solution

Xiangyun Qiu, Cornell University
Lisa W. Kwok, Cornell University
Hye Yoon Park, Cornell University
Jessica S. Lamb, Cornell University
Kurt Andresen, Gettysburg College
Lois Pollack, Cornell University

Copyright 2006, The American Physical Society


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 are essential for improving models of fundamental interactions in biological systems.