Of alginic acid

Algin occurs in all members of the class Phaeophjceae, brown seaweed, as a stmctural component of the cell walls in the form of the insoluble mixed calcium, magnesium, sodium, and potassium salt of alginic acid. 

The term alginate refers to the salt forms of alginic acid [9005-32-7] a copolymer of D-mannopyranosyluronic acid [56687-62-8] (1) and L-gulopyranosyluronic acid [56688-68-7] (2) residues. 

Figure 8.5 D-Mannuronic and L-guluronic repeat units of alginic acid...

D-Mannitol is not only a product of the hydrogenation of sucrose or of D-glucose but it is also a by-product of the fermentation of sugar to lactic acid and other special fermentations and is a by-product in the extraction of alginic acid from seaweeds. It is found in the sugar cane... 

When treated with 5% sulfuric acid for 1.5 hours at 150°, pectin and D-galacturonic acid give reductic acid in yields of approximately 10% it is also formed on treatment of alginic acid with acid.96,119 The original preparation from pectin has been improved by using ion-exchange techniques,110 and synthetic preparations have been developed.188... 

Rogovin, Treyvas and Shorygina [4] have examined the product of nitration of alginic acid obtained after 4 hr at 20°C by means of a mixed acid consisting of 48% HN03, 50% H3P04, and 2% P2Os. 

To explain the appreciable solubility of the product, Rogovin et al. suggest that the carboxylic groups of alginic acid are probably internally esterified with hydroxyl groups. Thus (as with pectic acid nitrates, see above) no cross-links can be formed of the type assumed by the same authors to exist in celluronic acids and in celluronic acid nitrates (see below). 

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... 

Figure 9. Kinetic plot for 0.01% (w v) B-lactoglobulin and 1.0% (w v) alginic acid adsorption on and desorption from germanium ATR crystal as a function of time of flow. Key D1548 cm 1 band of 13-lactoglobulin 1034 cm 1 band of alginic acid. (All data not shown for clarity.)...

Proof of the structure of the uronic acid was obtained by Hirst, Jones and Jones,46 who isolated the methyl glycoside methyl ester by methyla-tion of the products from the graded methanolysis of alginic acid. The tri-O-methyl-D-mannuronic acid was converted to the diamide of 2,3,4-tri-O-methyl-D-mannaric acid, which had previously been prepared from... 

The molecular weight of the sodium salt of alginic acid has been determined by measurements of osmotic pressure in sodium chloride solution.88 The n/C versus C curve was found to be independent of salt concentration for values between 0.2 N and 0.5 JV, and the slope of the curve was the same for a series of seven fractions with values of molecular weight between 48,000 and 186,000 (220-860 D-mannuronic acid units). Intrinsic viscosity measurements showed the coefficient a in the modified Staudinger s equation88 to be 1.0 and the approximate value of Km to be 15(10)-4. 

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