Galacturonic acid VOLUME

Concentration of galacturonic acid (pg/400 pi) Volume of 200 pg/rnl galacturonic acid Volume of water (pi) solution (pi) ... 

One peak is eluted at the void volume of the column and contained the bulk of neutral sugars and few galacturonic acid residues while the peak at the total volume contained almost pure oligogalacturonides. Therefore the same model of "hairy" regions and "smooth" regions also applied to these pectins. 

The partial specific volume of the monomeric unit in PGA was found to be approximately 3 per cent higher than the value of D-galacturonic acid... 

Fractions Total volume/eluate, ml D-galactu- neutral sugars, ronic acid, mg D-glucose mg protein, mg D-galacturonic acid % neutral sugars % protein content, %... 

Fig. 1. — Effect47 of Tomato Pectinesterase on the Activity of Pectate Lyase Acting on Highly Esterified Pectin. [Reaction mixtures contained 0.5% of D-galacturonan (broken line) or poly(D-galacturonic acid methyl ester) methyl glycoside (solid lines), 5 mM CaCl2, 33 mM phosphate buflFer (pH 7.0), and 0.25 unit of lyase in a final volume of 3.0 ml. In addition, the reaction mixture represented by the middle curve contained 0.031 unit of tomato pectinesterase in a final volume of 3.3 ml.] Reprinted, with permission, from M. Lee and J. D. Macmillan, Biochemistry, 9, 1930-1934 (1970). Copyright by the American Chemical Society.

Include with the five sets of termination tubes a series of five tubes to be used to establish the calibration curve. Place in the calibration tubes 0, 5, 10, 15, and 20 pi of 1 mM galacturonic acid. Then add 20 mM sodium acetate to bring the volume to 0.1 ml and add 1 ml BCA working reagent (final volume 1.1 ml/tube). 

The content of pectic substance in woody tissues is low because the volume of the pectic-containing layers is small. However, it occurs in fairly large amounts (10%) in the inner bark of black spruce 78). In soft tissues, like those of apple and other fruits devoid of secondary walls, the primary walls and middle lamella constitute a higher proportion of the total tissue, and the content of pectic substances is proportionately large. They are abundant in the rinds of citrus fruit, from which they are extracted as a by-product of citrus fruit production. Extraction is made usually with dilute hydrochloric acid solution. Crystalline salts of galacturonic acid have been... 

Most of the acids of the metabolism are found in trace amounts in ripe grape pulp (pyruvic, a-ketoglutaric, fumaric, galacturonic, shikimic, etc.). Must acidity, an important element of enological data, is essentially constituted by three acids tartaric, malic and citric acid (Volume 2, Section 1.2.2). It can vary from 3 to 10 g/1 in sulfuric acid or from 4.5 to 15 g/1 in tartaric acid, depending on the cultivar, the climate and grape maturity. Phosphoric acid is the preponderant inorganic anion. 

Figure 2. Fractionation of the pectin from the cold buffer extract of the ripe apple AIS on DEAE-cellulose. AUA, anhydrouronic acid, mg/ml Ve, elution volume, ml. The numbers in the figure indicate the neutral sugar residue content of the fractions, expressed as moles of neutral sugar residues/mole of galacturonate residues. (Reproduced with permission from reference 1. Copyright 1981 Carbohydrate Polymer).

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