Alginic acid conformation

N 143 "Conformational Energy Calculations on Alginic Acid I. Helix Parameters and Flexibility of the Homopolymers"... 

No serious attempt has as yet been made to solve, by modern methods, the crystal structure of any alginate, although x-ray diffraction data have been published122 and have been discussed elsewhere in this Series.27 It is sufficient to note that alginic acid and calcium alginate, both of which are known to form gels, are insoluble in water, and seem to pack in crystal lattices in the solid state. The conformation in salt solution is disordered, but very extended.1228... 

The structure of the crystalline alginic acid has been proved by X-ray difFraction studies, which gave evidence concerning the conformation of the hexopyranuronate components the n-mannopyranuronate residues exist in the CJ(n), and the L-gulopyranuronate residues in the same [JC(l)] conformation. ... 

Because the 3,6-anhydrogalactopyranose unit has the L-configuration, it exists in the 1C conformation. This is similar to the 3,6-anhydro-o-galactopyranose units of the k- and i-carrageenans and of the L-guluronic acid units of alginic acid. 

Davis, T.A., Llanes, F., Volesky, B. and Mucci, A. (2003) Metal selectivity of Sargassum spp. And their alginates in relation to their a-L-guluronic acid content and conformation. Environmental Science S. Technology, 37, 261-267. 

Conformational structures of segments of sodium alginate, containing /3-D-mannopyranosyl uronic acid, and ol-L-gulopyranosyl uronic acid and 2,8-o -colominic acid, containing / f-acetyl-o -D-neuraminic acid, linked (2- 8)... 

Polysaccharides. The most important member of this class of polysaccharides is alginate, a polysaccharide produced by seaweed and bacteria and widely used in the food industry. It is biosynthesised initially as a p-(1 4)-linked poly-mannuronic acid, by sequential transfer from GDP mannuronate. Some of the individual mannuronate residues are then epimerised at C5 to yield a-L-guluronate residues. The conformation of these guluronate residues is disfavoured by the axial OH on C2, the anomeric effect at Cl and above all by the now-axial carboxylate at C5 the C4 conformation, with the intersaccharide linkages now 1,4-diaxial, is adopted by the guluronate residues. 

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