Osmotic properties of DNA: Critical evaluation of counterion condensation theory - art. no. 021907

The Osmotic coefficient of B-DNA in water may, in dilute solutions, deviate by as much as 100% from predictions based on a simple line-charge "counter ion condensation" theory. In contrast, a cell model description of the ioni c atmosphere near a cylindrical polyelectrolyte predicts osmotic properties that are in surprisingly good harmony with all available experimental find ings over a wide range of DNA concentrations. We argue that the neglect of molecular features, such as finite radius, makes line-charge condensation t heory inapplicable at all but impractically low polyelectrolyte concentrati ons.