Determining the Locations of Ions and Water around DNA from X-Ray Scattering Measurements.

摘要: Nucleic acids carry a negative charge, attracting salt ions and water. Interactions with these components of the solvent drive DNA to condense, RNA fold, proteins bind. To understand biological processes, knowledge structure around nucleic is critical. Yet, because they are often disordered, water evade detection by x-ray crystallography other high-resolution methods. Small-angle scattering (SAXS) uniquely sensitive spatial correlations between solutes surrounding solvent. Thus, SAXS provides an experimental constraint guide or test emerging solvation theories. However, interpretation profiles nontrivial difficulty in separating signals each component: macromolecule, ions, hydration Here, we demonstrate methods for robustly deconvoluting signals, facilitating more straightforward comparison theory. Using data collected on absolute intensity scale short duplexes solution Na(+), K(+), Rb(+), Cs(+) counterions, mathematically decompose into (DNA, water, ions) validate decomposition using anomalous measurements. In addition, generate library physically motivated ion atmosphere models rank them agreement data. The best-fit have relatively compact atmospheres when compared predictions from mean-field Poisson-Boltzmann theory electrostatics. presented here provide valuable measurement global that can be used electrostatics theories go beyond approximation.