This Article Full Text Full Text (PDF) All Versions of this Article: biophysj.105.067918v1 89/4/2357    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Bathe, M. Articles by Tidor, B. Search for Related Content PubMed PubMed Citation Articles by Bathe, M. Articles by Tidor, B.

Osmotic Pressure of Aqueous Chondroitin Sulfate Solution: A Molecular Modeling Investigation

Mark Bathe ^*, Gregory C. Rutledge , Alan J. Grodzinsky ^*   and Bruce Tidor  

^* Departments of Mechanical Engineering, Biological Engineering Division, Chemical Engineering, and Electrical Engineering and Computer Science, the Massachusetts Institute of Technology, Cambridge, Massachusetts

Correspondence: Address reprint requests to Bruce Tidor, Tel.: 617-253-7258; E-mail: tidor{at}mit.edu.

The osmotic pressure of chondroitin sulfate (CS) solution in contact with an aqueous 1:1 salt reservoir of fixed ionic strength is studied using a recently developed coarse-grained molecular model. The effects of sulfation type (4- vs. 6-sulfation), sulfation pattern (statistical distribution of sulfate groups along a chain), ionic strength, CS intrinsic stiffness, and steric interactions on CS osmotic pressure are investigated. At physiological ionic strength (0.15 M NaCl), the sulfation type and pattern, as measured by a standard statistical description of copolymerization, are found to have a negligible influence on CS osmotic pressure, which depends principally on the mean volumetric fixed charge density. The intrinsic backbone stiffness characteristic of polysaccharides such as CS, however, is demonstrated to contribute significantly to its osmotic pressure behavior, which is similar to that of a solution of charged rods for the 20-disaccharide chains considered. Steric excluded volume is found to play a negligible role in determining CS osmotic pressure at physiological ionic strength due to the dominance of repulsive intermolecular electrostatic interactions that maintain chains maximally spaced in that regime, whereas at high ionic-strength steric interactions become dominant due to electrostatic screening. Osmotic pressure predictions are compared to experimental data and to well-established theoretical models including the Donnan theory and the Poisson-Boltzmann cylindrical cell model.