Uronic acid content

Recently, the alkah-soluble hemicelluloses of hardwood dissolving pulps have been investigated [28]. Their composition and molecular properties depended on the pulp origin and steeping conditions. The MGX of the j8-fraction from press lye had a low uronic acid content (ratio of MeGlcA to Xyl is about 1 20). The molecular weight of the hemicellulose fractions varied between 5000 and lOOOOg/mol. 

Tomato fruits (Lycopersicon esculentum Mill. var. Castlemart ) were collected from vines grown in the field at the University of California, Davis. Pericarp discs were cut from surface sterilized MG stage fruit (10). Droplets (10 n ) of test solutions (see below) were applied to the cut surface of discs and disc ethylene production was measured as described previously (11). The amounts of test materials used were based on colorimetric assay (6) of uronic acid content. 

Table 2. Permeability, flux, and uronic acid content of PE extract permeated at pH 8.0 followed by permeation at pH 3.8 ...

Uronic acid content was determined as anhydro-uronic acid (AUA) by the automated colorimetric /n-hydroxydiphenyl assay [2,3,6] using an auto-analyser (Skalar Analytical BV, Breda, The Netherlands). Corrections were made for interference by neutral sugars present in the sample. 

E3.3 Determination of the Uronic Acid Content of Plant Cell Walls Using a Colorimetric Assay... 

Selvendran, R.R., March, J.F.. and Ring. S.G. 1979. Determination of aldoses and uronic acid contents of vegetable fiber. Anal. Biochem. 96 282-292. 

Cell walls and cell wall fractions are first hydrolyzed using the method of Ahmed and Labavitch (1977) and the uronic acid content estimated using the method of Filisetti-Cozzi and Carpita (1991). 

Colorimetric Assay of Uronic Acid Content of Cell Walls... 

It may be necessary to prepare an alternative dilution series depending on the uronic acid content of your samples. 

Additional reagents and equipment for isolating pectin (unite3.i) and determining total uronic acid content (UN1TE3.3)... 

Determine total uronic acid content from an aliquot of each fraction using the method described in unit E3.3. 

For a sample calculation, a 30-mg sample was found to have 30.1% uronic acid content (UNITE3.3). Therefore, it had 9.03 mg or 0.051 mmol uronic acid. (The molecular weight or uronic acid is 176 g/mol.) The amount of methanol in this sample, as calculated from the standard curve, was 1.2 mg/ml. Therefore, in 1 ml of sample in isopropanol/NaOH, there would be 1.2 mg or 0.0375 mmol methanol. (The molecular weight of methanol is 32.04 g/mol.) Therefore, the degree of methylation = (0.0375/0.051) x 100 - 74%. 

PGase activity assay, 335-348 uronic acid content, colorimetric assay, 735-738... 

The presence of uronic acid groups significantly reduces the hydrolysis rate of glycosidic linkages (Table 2). Thus, high yields of aldobiuronic acid dimers were obtained on partial hydrolysis of xylans [18, 19, 242]. The hydrolysis rate of different hardwood xylans was closely related to their uronic acid content [257]. A higher stability of softwood xylan as compared to... 

Pellerin, P, Vidal, S., Williams, R, Brillouet, J. M. (1995). Characterization of five type II arabinogalactan-protein fractions from red wine of increasing uronic acid content. Carbohydr. Res., 277, 135-143. 

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