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Uronic acids, in polysaccharides

The uronic acids in polysaccharide fraction I (Table 2) were determined colorimetrically with m-hydroxybiphenyl (15). [Pg.681]

The quantitative determination of uronic acids in polysaccharides is complicated by lactonization, and these problems have been carefully examined by Blake and Richards.26,98 In the course of these studies, D-glucuronic acid was reduced to D-glucitol, which was characterized as the hexaacetate.98 As uronic acid residues in a polysaccharide may be reduced relatively easily,465,466 determination as the alditol provides an alternative method of analysis.461,468 This procedure is most valuable when different uronic acids are present in... [Pg.77]

G. O. Aspinall, Reduction of uronic acid in polysaccharides, Methods Carbohydr. Chem., 5 (1965) 397-400. [Pg.291]

As investigations with polysaccharides of microbiological, plant, and animal origin revealed the presence in these substances of uronic acids, it became necessary to know more about the acids. Moreover, the occurrence of uronic acids in plant gums and pectic substances, and the structures of urinary... [Pg.13]

In model experiments,205 it was found that concentration of an aqueous solution of the aldonic acids in the presence of hydrochloric acid gives exclusively the 1,4-lactones, which, on subsequent trimethyl-silylation, give only one peak on the chromatogram. This method was successfully employed for the separation of D-galacturonic, D-glucuronic, and D-mannuronic acids. Of the 1,4-lactones examined, only the trimethylsilyl ether of D-mannono-1,4-lactone was obtained in crystalline form. However, all of the derivatives showed characteristic differences in their infrared spectra in the range of 1500 to 600 cm"1. When this method was applied to the determination of uronic acids in a variety of polysaccharides,205 it was impossible to find any hydrolytic conditions under which the uronic acids were quantitatively released and then reduced, a problem experienced by other workers.20 The method was, however, successful in affording a qualitative, microscale procedure for the identification of hexuronic acids (which otherwise are difficult to detect). [Pg.71]

Uronic acid in the form of galacturonic acid is a major component of the pectic polysaccharide rhamnogalacturonan, which is present in large amounts in the cell walls of most fruits and vegetables. Small amounts of glucuronic acid and 4-O-methylglu-curonic acid have also been detected in cell walls. [Pg.735]

The chemistry of these polysaccharides is dominated by partial esterification of the total number of carboxyl groups. The sequence of uronic acids in the primary structure is occasionally interrupted by rhamnose, and there is usually a trace of acetyl and phenolic substituents. Models developed from experimental data considered neutral side chains with DP = 2-10 (De Vries et al., 1982). These 1,4-a-linked linear uronans are susceptible to alkali—more so if the C-6 hydroxyl is esterified, but exceptionally acid-stable when this site is unsubstituted. Dispersion stability is less at higher DP. Uronans are endowed with strong dye-fixing and mineral-sequestering properties because of their charged surface. [Pg.173]

Calcium is coordinated between certain uronic acid-containing polysaccharides (VIII), which can explain the tight binding of calcium and other multivalent ions in polysaccharide stmctures, and also how bivalent ions can induce gel formation in acidic polysaccharides such as alginic acid solutions. [Pg.288]

J. E. Scott and R. J. Harbinson, Periodate oxidation of acid polysaccharides. II. Rates of oxidation of uronic acids in polyuronides and acid mucopolysaccharides, Histochemie, 19... [Pg.245]

Keratan sulfate is very much the odd one out in the polysaccharides embraced by the term glycosaminoglycan since it contains no uronic acid. In place of the uronic acid residue in other glycosaminoglycans, there is a neutral hexose unit— n-galactose. The second component monosaccharide is normal being a 2-acetamido-2-deoxyhexose. The repeating disaccharide unit of keratan sulfate is -0-jS-D-galactopyranosyl-(l- 4)-O- (2-acetamido-2-deoxy- 3-D-glucopyranosyl 6-sulfate) - (1 3) - ( VIII)... [Pg.12]

Polyuronides macromolecular compounds found in plants, consisting of units of uronic acids in the pyr-anose form (see Carbohydrates). The main components are o-glucuronic acid, o-galacturonic acid and D-mannuronic acid. P. contain free carboxyl groups and are consequently more strongly hydrated than polysaccharides formed from neutral monosaccharides. Examples are pectins, alginic acid and plant mucilages. [Pg.533]

Methyl 2,2, 3,3 4, 6 -hexamethyl-j8-maltoside (4) has been converted to the mixture of alditol glycosides (5) as outlined in Scheme 1, which can form the basis of a method for the specific degradation of uronic acid-containing polysaccharides, mass spectrometry showing the site of linking, and n.m.r. spectroscopy the glycosidic configuration. ... [Pg.139]

The isolation of uronic acids from polysaccharides is not easy. Some of the linkages are very resistant to acid hydrolysis. Sulfuric acid (4%) at 120 for 10 to 24 hours 56) is often required. This harsh treatment may decompose the products considerably, and the yields are generally low. Cold 80 % sulfuric acid, 3 % oxalic acid at 100°, boiling 98 % formic acid 8 hours at 100° (for methylated alginic acid), and boiling 90% formic acid have been used for the hydrolysis of alginic acid (57). In the pectin field, enzymic hydrolysis has been used for the isolation of galacturonic acid the procedure is very mild and excellent yields are obtained. [Pg.315]

The aldobiouronic acids liberate carbon dioxide and form furfural in a manner similar to the uronic acids. With polysaccharide materials, the formation of carbon dioxide is considered very strong evidence for the presence of uronic acids. The evidence for a biological formation of pentosan material by the decarboxylation of uronic acid groupings is very weak, however, for some polyuronide materials contain both arabofuranose and galactopyranose units (see Chapter XII). [Pg.323]

When more than two types of sugars are combined to produce a polysaccharide, they usually form a branch-on-branch structure exemplified by D in Fig. 1. Even here, some semblance of a simplifying order seems to exist. Thus, it is common to find hexose sugars and perhaps uronic acids in the main or central branches while the pentose sugars, D-xylose and L-arabinose, are in the side branches. [Pg.646]

The primary wall is a continuous, fairly pliable membrane forming the outside surface of the plant cell. It is about 0.5 micron in thickness and, thus, is only a small part of the cell. It is heavily lignified but is predominantly carbohydrate, with pectin, uronic acid - containing polysaccharides, and xylan or mannan in abundance and with cellulose in lesser amounts. For the most part the very long cellulose molecules are grouped into many fine threads (Fig. 3) which form a meshlike but coherent arrangement. They are intricately woven and mixed with the other polysaccharides,... [Pg.660]


See other pages where Uronic acids, in polysaccharides is mentioned: [Pg.239]    [Pg.204]    [Pg.213]    [Pg.239]    [Pg.204]    [Pg.213]    [Pg.250]    [Pg.43]    [Pg.72]    [Pg.75]    [Pg.247]    [Pg.54]    [Pg.101]    [Pg.216]    [Pg.24]    [Pg.1167]    [Pg.262]    [Pg.69]    [Pg.88]    [Pg.187]    [Pg.1416]    [Pg.1420]    [Pg.2339]    [Pg.289]    [Pg.155]    [Pg.141]    [Pg.168]    [Pg.680]    [Pg.33]    [Pg.34]    [Pg.472]    [Pg.255]    [Pg.186]    [Pg.77]    [Pg.661]    [Pg.203]   
See also in sourсe #XX -- [ Pg.230 , Pg.239 , Pg.240 , Pg.241 ]




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2- uronate

Acidic polysaccharides

Uronates

Urones

Uronic

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