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  • Title: Unperturbed dimensions of Carrageenans in different salt solutions.
    Author: Marcelo G, Saiz E, Tarazona MP.
    Journal: Biophys Chem; 2005 Mar 01; 113(3):201-8. PubMed ID: 15620505.
    Abstract:
    Commercial samples of kappa-, iota-, and lambda-carrageenans were studied by means of Size Exclusion Chromatography with dual detection, i.e. employing a Refractive Index (concentration sensitive) and Multiangle Light Scattering (size sensitive) detectors. The eluent was water containing 0.1 M concentration of different ionic salts, namely LiCl, NaCl, KCl and NaI, with the exception of kappa-carrageenan that aggregates in presence of KCl. Molecular weight distributions and averages, coefficients of the scaling law of molecular dimensions and unperturbed dimensions were thus obtained from a single polydisperse sample of each polymer. Measurements were performed at 25 degrees C and all the systems were above theta conditions with values of the q exponent of the scaling law ranging from 0.51 to 0.59. Extrapolation to unperturbed conditions provides values of the characteristic ratio C(N)=56+/-1 and 40+/-5 respectively for lambda- and iota-carrageenans regardless of the ionic salt employed. However, kappa-carrageenan gives C(N)=31, 35 and 59, respectively, in presence of LiCl, NaCl and NaI, which clearly indicates that this polymer behaves on a different way in presence of NaI than with the other two salts. A tentative explanation of this difference is provided.
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