Ion Competition in Ordered DNA arrays in the Attractive Regime

Quantitative knowledge of electrostatic interactions is of fundamental importance for many classes of biomolecules and biological processes. Acquiring such knowledge is challenged by inherent complexities such as the long-range nature of electrostatic forces, the non-linear screening of ubiquitous ions, and the involvement of a large number of solvent molecules. Here we report our recent work to address some of the key questions by interrogating electrostatics-governed ordered nucleic acids arrays and bringing together a set of quantitative tools to elucidate the role of each of the electrostatic factors: ion, water, and charged surface. Specifically, we will present measurements and modeling of the spacings between DNA strands and the numbers of interstitial competing ions in the attractive regime. Our results indicate a linear relation between the partition of interstitial ions and the magnitude of inter-DNA attraction, which will be discussed in the context of current theories of electrostatic interactions.