Oligosaccharide methylated, hydrolysis

Cello- and malto-oligosaccharides up to nonasaccharides in the presence of various metal salts have been analyzed by f.a.b.-m.s. The structures of two methyl alduronates obtained by flash hydrolysis of wood chips was deduced by using f.a.b.-m.s., n.m.r. spectroscopy, and sugar analysis. ... 

Oligosaccharides were isolated from PMII by weak acid hydrolysis and separation by SEC and HPAEC-PAD. The isolated oligosaccharides were desalted, reduced and methylated. GC-MS analysis of the partially methylated alditol acetates has been used to reveal the structure of the oligosaccharides. 

The partially methylated monosaccharides obtained on depolymerization of the permethylated sample are preferably analyzed as acetates by g.l.c.-m.s., as shown by Bjomdal and coworkers.41,42 The neutral sugars and the amino sugars obtained in acetolysis-acid hydrolysis are reduced, and acetylated for the analysis, and the amino-hexitol and the neuraminic acid residues are acetylated after methanolysis. Identification with the aid of g.l.c.-m.s. has been described for all of the common components of protein- and lipid-linked glycans and oligosaccharides from animal cells, namely, the neutral sugars,41-43 hexitols,44 hexosamines,29,43,45,46 aminohexitols,31,32 and neuraminic acids.33,34,47... 

Methylation analysis Permethylation of intact oligosaccharides Hydrolysis of glycosidic linkages Reduction to monosaccharide alditols Acetylation of free hydroxyl groups previously involved in link-... 

The methylation technique consists of total methylation of the oligosaccharide, followed by hydrolysis to the partially methylated monosaccharide units, and determination of the unmethylated positions in each unit, these being the positions of linkage between units. 

Xyloisosaccharinic acid [2,4-dihydroxy-2-(hydroxymethyl)butanoic acid] is one of the major, alkaline-degradation products of wood xylan, in particular, that of birch. The disaccharide, 2-O-D-xylopyranosyl-L-arabinose, which was isolated as a hydrolysis product of corn-cob hemicellulose, is readily degraded at 100° in 15 mM Ca(OH)2 to acidic products, primarily saccharinic acids. Xylan oligosaccharides from corn-cob hemicellulose produced 2,4-dihydroxy-2-(hydroxymethyl)buta-noic acid when exposed to 0.02 M Ca(OH)2 at 25°. However, it was noted that the xylan, itself, was stable at 100° in Af NaOH. The major acidic component of the hemicellulose fraction of slash pine Pinus el-liotti) after acid hydrolysis was identified as 4-O-methyl-D-glucuronic... 

The methyl ester of operculinic acid E was obtained by basic hydrolysis and methylation of the crude resin glycoside mixture of 7. murucoides. Mumcoidins XII (53) and XIII (54) afford operculinic acid E as their oligosaccharide core. The lactonization site was placed at C-3 of the first rhamnose unit. These resin glycosides contain an esterifying residue that is composed of n-dodecanoic or (25)-methylbu-tyric acids at the C-2 or C-3 positions on the second rhamnose unit of the oligosaccharide core and (25)-methylbutyric acid at C-4 on the third rhamnose (30). 

Figure 4. Total ion chromatogram of the methylated mono/oligosaccharide obtained by the partial acid hydrolysis of the bran arabinogalactoglu-curonoxylan.

Figure 2. Hydrolysis products of beechwood O-acetylglucuronoxylan (Fig. 2a), beechwood glucuronoxylan (Fig. 2b), and wheat straw arabinoxylan (Fig. 2c), as analyzed by gel permeation chromatography. The hydrolysis was carried out at pH 5 at 45°C for 24 h using 10.000 nkat of the 20 kDa xylanase of T. reesei. X = xylose X2 = xylobiose Xmga — 4-O-methyl-glucuronosyl substituted xylo-oligosaccharides X = xylo-oligosaccharides DP > 20.

Structural studies on the oligosaccharide derivatives obtained by partial, acid hydrolysis of fully methylated polysaccharides often furnish valuable information on the positions at which the oligosaccharides were linked in the original polysaccharide. When the folly methylated Klebsiella O group 9 lipopolysaccharide,27 which contains D-galactopyranose and D-galactoforanose residues, was subjected to mild, acid hydrolysis, and the product reduced with lithium aluminum deuteride and remethylated with trideuteriomethyl iodide, a good yield of the disaccharide derivative 10 was obtained. 

The structures of oligosaccharides and polysaccharides are usually determined by a combination of methods specific enzymatic hydrolysis to determine stereochemistry and produce smaller fragments for further analysis methylation analysis to locate glycosidic bonds and stepwise degradation to determine sequence and configuration of anomeric carbons. 

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