Guluronic acid, alginate

Alginates are made up of long chains of two monomers guluronic acid and mannuronic acid. The chains can be made of all one monomer or mixtures of both. The stems of kelp are made of chains with more guluronic acid, and the leaves (fronds) have more mannuronic acid. Guluronic chains bind tightly to calcium in mannuronic chains the calcium is more easily replaced by sodium, allowing the fibers to swell easily. 

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. 

Page 243, line 6. L-Guluronic acid has been isolated from alginic acid.264(d Page 244, line 5 up. Read coenzymes.259W... 

Formation of L-guluronic acid, a component of the alginic acid-like polysaccharide produced by P. aeruginosa and Azotobacter vinelandii, requires special comment. In this case, a polymer built from /3-(l- 4)-linked D-mannosyluronic acid residues serves as an intermediate in the biosynthesis.204,205 Part of the D-mannosyluronic acid residues in the polymer is subjected to an epimerization at C-5 catalyzed by an exocellular enzyme of the micro-organism,205-207 producing a polysaccharide composed of structural blocks that contain only D-mannosyluronic acid or only l-gulosyluronic acid residues, as well %s some having both. The mechanism of the epimerization remains unclear. 

D-Mannuronic acid (36) constitutes the major component of alginic acid, the main polysaccharide of the brown algae, in which L-guluronic acid (37) is also found. The ratio of D-mannuronic acid and L-guluronic acid can vary with the algal species, the type of tissue, and the age of the plant. In the case of Laminaria hyperborea, L-guluronic acid is the major component.130... 

Noncovalent wrapping with polysaccharides is another commonly used approach in the carbohydrate functionalization and solubilization of carbon nanotubcs.39-42 For example, Liu et al. used alginic acid (AA), a natural polysaccharide constituted with repeated (3-D-mannuronic acid ((3M) and a-L-guluronic acid (aG) segments, to... 

Residues of alginate [/3-d-(1— 4)-mannuronan or poly-(D-mann-uronic acid] are converted into L-guluronic acid residues by D-mannuronan 5-epimerase, with incorporation of tritium from water-f. For this epimerization, in which C-4 cannot be oxidized, an enolization of the carbonyl group of the carboxylic acid has been proposed.148"... 

Figure 14.33. Structures of guluronic acid and mannuronic acid and the 100-MHz l3C spectrum of alginic acid. (From ref. 8. Reprinted with permission of Elsevier Science S.A.)...

---