The Influence of Osmolytes on Electrostatic Interactions Among DNA Duplexes

Abstract

Osmolytes, which function as a vital component of the cellular stress response, are small, chemically diverse, intracellular organic solutes. Protecting osmolytes enhance protein stability via preferential exclusion, where denaturation of the protein in the presence of the osmolyte is less favorable than in an aqueous environment. Thus, the correct ratios of protecting to non-protecting osmolytes and protecting osmolytes to ions are critical to maintain protein structure and protein-nucleic acid interactions. In contrast to the effects of osmolytes on protein stability, structure, and function, there is much less understood concerning the effects of osmolytes on nucleic acids. Although non-protecting osmolytes can destabilize both protein and nucleic acid structures, protecting osmolytes have different effects depending on the complexity of the nucleic acid structure. Furthermore, the influence of osmolytes on the ion atmosphere surrounding nucleic acids is not well understood. As a first step in quantifying the effects of osmolytes on nucleic acid electrostatics we used small angle x-ray scattering (SAXS) techniques to monitor 25-bp DNA duplexes and their interactions in the presence and absence of sucrose, a protecting osmolyte and important contrast matching agent in SAXS studies of protein-nucleic acid complexes. Results will be discussed.