title: Counterion diffusion in heparin solutions.
abstract: The physiological importance of heparin is due to its strong interaction with bivalent counterions, especially Ca2+. A diffusional approach of this property is presented in this article: the observable is the self-diffusion coefficient of the counterions, as a function of the ratio of the polyelectrolyte over the added salt concentrations. All the results are in agreement with a simple "quasi-chemical model" in which two different states are assumed for the counterions: "free" or "bound." The proportions of these two types of ions are calculated according to the distribution function of the counterions around the polyion. We assume that those of counterions located at a distance closer than a, the characteristic distance, are bound; the others are free. The ionic distribution function is evaluated by a numerical integration of a cell model Poisson-Boltzmann equation. Finally, this model leads to a very good agreement with the experimental results, if the radius of heparin polyion is assumed to be 6 and 10 A.
authors.forename: P
authors.initials: P
authors.lastname: Tivant
authors.forename: A
authors.initials: A
authors.lastname: Perera
authors.forename: P
authors.initials: P
authors.lastname: Turq
authors.forename: L
authors.initials: L
authors.lastname: Belloni
mesh_terms: D004058:Diffusion; D006493:Heparin; D007477:Ions; D008962:Models, Theoretical; D012996:Solutions
chemical_list: D007477:Ions; D012996:Solutions; D006493:Heparin