ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
The static structure of solutions of DNA fragments is investigated using integral equation theory. The solution is modeled as a four-component system with DNA molecules, bound counterions, free counterions, and coions, all of which are treated explicitly. Each DNA fragment is modeled as a shish-kebab chain with three kinds of sites, i.e., charged sites, neutralized (protonated) sites, and sites with bound counterions. The partial structure factors are obtained using a generalization of the polymer reference interaction model. The undetermined parameters in the model, namely the fraction of protonated and bound sites, are obtained by fitting theoretical predictions for the polymer–polymer and polymer–counterions structure factors to experimental data. It is found that a large majority of counterions is localized near the DNA molecules due to counterions binding and protonation. The bound counterions make a dominant contribution to the total scattering from counterion species. The best fit is obtained when each DNA molecule contains about 22% protonated sites and 53% counterion occupied sites, i.e., the effective DNA charge fraction is about 0.25. This DNA charge fraction is consistent with electrospray ionization and DNA titration experiments. © 2002 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.1448492
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