Uronic acids spectroscopy

Infrared spectra of glycosaminoglycans in D20 and DC1 were used165 for quantitative evaluation of the uronic acid and acetamido groups in this class of polysaccharide. The results showed that i.r. spectroscopy of compounds in D20 solution provides a simple, quantitative basis for examination of ras(COJ) and amide I bands in heparin and chondroitin 4-sulfate. In DC1, analysis was based on p(C02H) and amide I bands which were well resolved. The apparent acid-dissociation constants of the studied polysaccharides were estimated from the absorbance of p(C02) or p(C02H) bands, or both, at different pH (pD) values. 

Uronic Acid Composition and Block Length. A sample containing 75 mg alginic acid was first suspended in a small volume of D2O, then fully neutralized by titration with 1.0 M NaOD. D2O was added to achieve a final concentration of 25 mg alginic acid/mL D2O. Equilibration of at least one hour was allowed prior to NMR acquisition. The uronic acid composition was determined by NN spectroscopy, with a 2 s pulse repetition time and 16,000 scans. The reported composition and block lengths were the average of two determinations. 

Free acetic acid can be determined by GLC (Shelley et al., 1963). An estimate of 0-acetyl content can be obtained from IR spectrometry (Bacon et al., 1975). However, if the preparation examined also contains esterified uronic acids, IR spectroscopy is of limited value as both carbox-ylate and 0-acetyl esters absorb at the same wavelength (1730 cm ). 

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. ... 

Bociek, S. M. Welti, D. The quantitative analysis of uronic acid polymers by infrared spectroscopy. Carbohyd. Res. 1975,42,217-226. 

The aim of the present study was to investigate die structural composition of the hemicellulose fractions, e.g. the presence of uronic acid side chains by means of MALDl-MS analysis, FT-IR- and solid-state NMR-spectroscopy. For comparison also a softwood-derived starting material was used. 

Reviews have appeared on the use of high resolution n.m.r. spectroscopy in the structural determination of complex carbohydrates and of some 3-0-, 4-0-, and 3,4-di-O-glycopyranosyl-substituted methyl D-gtycopyranosides. The latter publication includes complete assignments of and C-n.m.r. resonances as well as conformational studies using HSEA effect theory. The application of various njnj. techniques (multi-relayed correlation, H- H-correlated, triple quantum field H- H-correlated and H- H homonuclear Hartmann Hahn spectroscopy) to carbohydrate analysis has been reviewed in Japanese, and in a further Japanese review the interactions of metal ions with uronic acids and amino sugars as observed by the lanthanide-probe n.m.r. method are discussed/... 

Coimbra, M. A., Barros, A., Barros, M., Rutledge, D. N. Delgadillo, I. (1998) Multivariate analysis of uronic acid and neutral sugars in whole pectic samples by FT-IR spectroscopy. Carbohydrate Polymers, 37, 241-248. 

The conditions under which HC1 formed in acidified sodium chloride droplets would be expected to enter the gas phase have been treated by Clegg and Brimble-combe (1990). Cadle and co-workers (Robbins et al., 1959 Cadle and Robbins, 1960) observed that NaCl aerosols in the presence of 0.1-100 ppm NOz at relative humidities of 50-100% lost chloride ion from the particles. They ascribed this to the formation of nitric acid from NOz, followed by reaction (1). Schroeder and Urone (1974) subsequently suggested that NOz could react directly with NaCl to produce gaseous nitrosyl chloride, C1NO, which they observed using infrared spectroscopy stoichiometrically, this is represented as... 

The sequence and composition of uronate residues in intact alginate samples have been determined by high resolution H n.m.r. spectroscopy. Problems encountered owing to the viscosity of the samples were overcome by controlled and slight depolymerization before n.m.r. at 90 °C. The D-mannuronic acid L-guluronic acid molar ratio was obtained from the intensities of the signals from... 

Hashimoto and Neeman (1963) have obtained pure crystalline estriol 16a-glucosiduronic acid from third trimester human pregnancy urine, completely characterized it and converted it to two derivatives. Infrared spectroscopy was used in the identification of these compounds, methyl(3,17/S-dimethoxyestra-l,3,5(10)-trien-16a-yl-2, 3, 4 -tri-0-methyl-)S-D-glucopyranosid) uronate, and methyl (3-methoxy-17/S-acetoxyestra-l,3,5(10)-trien-16a-yl-2, 3, 4 -tri-O-acetyl-)5-D-glucopyranosid)-uronate. 

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