Extent of charge screening in aqueous polysaccharide solutions.
The absorption optical system of a Beckman XL-I ultracentrifuge has been used to monitor the Donnan distribution of ions in polysaccharide solutions dialyzed against sodium phosphate buffer (pH 6.8, I 0.08) supplemented with 0.2 mM chromate as an indicator ion. For dextran sulfate, heparin, and polygalacturonate, the effective net charges are shown to be only one-third of those deduced from the chemical structures--a reflection of charge screening (counterion condensation) in aqueous polyelectrolyte solutions. Whereas the extent of charge screening for the first two polysaccharides agrees well with theoretical prediction, the disparity in the corresponding comparison for polygalacturonate reflects partial esterification of carboxyl groups, whereupon the experimental parameter refers to the effective charge per hexose residue rather than the effective fractional charge of each carboxyl group.
Winzor
Donald J
DJ
Department of Biochemistry, University of Queensland, Brisbane, Queensland 4072, Australia, and National Center for Macromolecular Hydrodynamics, University of Nottingham, Sutton Bonington, LE12 5RD, UK. d.winzor@mailbox.eq.edu.au
Carrington
Lyle E
LE
Deszczynski
Marcin
M
Harding
Stephen E
SE
D001672:Biocompatible Materials / Q000737:chemistry*; D016264:Dextran Sulfate / Q000737:chemistry; D003956:Dialysis; D004563:Electrochemistry; D005690:Galactose / Q000737:chemistry; D006493:Heparin / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007477:Ions; D046911:Macromolecular Substances / Q000737:chemistry; D008956:Models, Chemical; D010710:Phosphates / Q000737:chemistry; D011134:Polysaccharides / Q000737:chemistry*; D012996:Solutions; D014461:Ultracentrifugation
D001672:Biocompatible Materials; D007477:Ions; D046911:Macromolecular Substances; D010710:Phosphates; D011134:Polysaccharides; D012996:Solutions; D006493:Heparin; D016264:Dextran Sulfate; D005690:Galactose