M. Ciszkowska et I. Kotlyar, Conductometric detection of coil-to-helix transition of anionic polysaccharides. kappa-carrageenan, ANALYT CHEM, 71(22), 1999, pp. 5013-5017
The conformational coil-to-helix transition of an ionic polysaccharide, kap
pa-carrageenan, as effected by temperature and concentration of the polyion
, was studied using conductance measurements in solutions of low ionic stre
ngth. Interactions between counterions, Na+, and polyions during such a tra
nsition were quantified by the ratio of the diffusion coefficient of Na+ co
unterions in the pobelectrolyte solution (kappa-carrageenan sodium salt) to
that in the solution without polyelectrolyte (NaCl), Structural characteri
zation of kappa-carrageenan conformers, expressed by the charge separation
distance, was performed based on Manning's theory for polyelectrolytes. The
conformational transition was a reversible coil-to-double helix process re
sulting from temperature decrease. This process did not depend on the conce
ntration of kappa-carrageenan for the concentration range from 10 to 40 mM,
The determined charge separation distance for kappa-carrageenan in solutio
n was 0.89 and 0.40 nm for a coil and a double-helix form, respectively.