Analysis of Partially Methyl-Esterified Galacturonic Acid Oligomers by High-Performance Anion-Exchange Chromatography and Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry

Two methods were developed to detect partially methyl-esterified galacturonic acid oligomers, generated by endopolygalacturonase treatment of a 30% methyl-esterified pectin. The enzyme digest was shown, by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, to contain sodia...

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Bibliographic Details
Published in:Analytical biochemistry 1998-03, Vol.257 (2), p.195-202
Main Authors: Daas, Piet J.H., Arisz, Peter W., Schols, Henk A., De Ruiter, Gerhard A., Voragen, Alphons G.J.
Format: Article
Language:English
Subjects:
Chromatography, Ion Exchange
Esters
Food Chemistry and Microbiology
Hydrogen-Ion Concentration
Levensmiddelenchemie en -microbiologie
Pectins - analysis
Pectins - chemistry
Pectins - metabolism
Polygalacturonase - metabolism
Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
VLAG
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Summary:Two methods were developed to detect partially methyl-esterified galacturonic acid oligomers, generated by endopolygalacturonase treatment of a 30% methyl-esterified pectin. The enzyme digest was shown, by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, to contain sodiated galacturonic acid oligomers with a degree of polymerization of 2–12, containing 0–6 methyl esters. Galacturonic acid (monomer) could not be detected because of matrix ions interference in the low mass region. Using high-performance anion-exchange chromatography, with a sodium acetate gradient at pH 5.0 and postcolumn sodium hydroxide addition to allow pulsed amplified detection, a complex elution profile was obtained with the endopolygalacturonase-treated 30% methyl-esterified pectin. All the components eluted before nonesterified tetragalacturonic acid. The partially methyl-esterified oligogalacturonic acids eluted in a discernible series of oligomers with an identical number of nonesterified carboxylic acid groups; the large, more esterified oligomers eluted before small, less esterified oligomers. The methyl esters may hinder the interaction of the neighboring carboxylic acid groups with the anion-exchange resin, thereby giving the components an apparent lower overall negative charge.
ISSN:0003-2697
1096-0309
DOI:10.1006/abio.1997.2554