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Counterion diffusion in heparin solutions
Author(s) -
Tivant P.,
Perera A.,
Turq P.,
Belloni L.
Publication year - 1989
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.360280609
Subject(s) - counterion , chemistry , polyelectrolyte , ion , ionic radius , diffusion , chemical physics , ionic bonding , thermodynamics , poisson–boltzmann equation , statistical physics , polymer , physics , organic chemistry
The physiological importance of heparin is due to its strong interaction with bivalent counterions, especially Ca 2+ . 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 Å.