Conformational transition of .kappa.-carrageenan in aqueous solution

Abstract

The interaction of Cs+ ions with c-carrageenan in aqueous solution was studied by using spectroscopic (133Cs NMR, optical rotation, and turbidimetry) and thermodynamic (isothermal microcalorimetry and dilatometry) techniques. All data collected seem to confirm the previous evidence of the occurrence of a conformational transition, induced by temperature and/or ionic strength. From NMR and calorimetry data the relative amount of species in equilibrium (disaccharide repeat units present as disordered coil, single helices, and dimers of single helices) is computed. Comparison of calorimetric and dilatometric data with theoretical predictions allows one to discriminate between overall and purely electrostatic contributions to the binding of Cs+ ions by x-carrageenan.

The extraction, structure, and gelling properties of hybrid galactan from the red alga Furcellaria lumbricalis (Baltic Sea, Estonia)

“…Gel formation in an aqueous solution is a complex process that depends not only on polysaccharide structure, polymer concentration, and temperature, but also on the presence of co-and counter-ions (Morris et al 1980;Meunier et al 2001). Certain cations (typically K + for κ-carrageenan and furcellaran, and Ca 2+ for ι-carrageenan) have been found to induce conformational changes in the polymer structure with an initial coil-to-helix transition, which may be followed by the aggregation of these helices to form a gel (Rochas and Rinaudo 1984;Paoletti et al 1985). The dependence of the gelling properties upon an ionic factor has widely been investigated, discussed, and (Borgström 1997;Rinaudo 2005;Piculell 2006).…”

Comparative studies on the conformational change and aggregation behavior of irradiated carrageenans and agar by dynamic light scattering

“…Metal ions such as K + , Na + , Li + , and Ca 2+ are said to affect these structure transformations to varying degrees. The conformational associative properties of carrageenan and agar have extensively been studied using several methods including light scattering techniques [1][2][3][4][5][6][7][8][9][10][11][12][13]. Decrease in molecular weight by degradation either by sonolysis or ionizing radiation can also affect so much these transitions [14][15][16].…”

Gel-forming structures and stages of red algal galactans of different sulfation levels

“…(Therkelsen 1993). Gel formation in an aqueous solution is a complex process that depends on polysaccharide structure, polymer concentration and temperature, but also on the presence of co-and counter-ions (Morris et al form a gel (Rochas and Rinaudo 1984;Paoletti et al 1985). The final gel structure is often determined by mutual interactions between conformational transition, molecular cross-linking and phase-separation processes.…”