Oligosaccharides hydrolysis, acid

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 identification of L-iduronic acid as the major glycuronic acid constituent of heparin proved to be a much slower process than the identification of the amino sugar residue. Although this compound was detected in acid hydrolyzates of heparin116117 and heparin oligosaccharides,118 its yield was usually poor, because of the drastic conditions used for the acid hydrolysis (which are known to lead to extensive destruction of uronic acid).119120 Also, L-iduronic acid escaped detection as L-idose in the hydrolyzates of carboxyl-reduced heparin, probably because L-idose is readily converted into 1,6-anhydro-L-idose under the usual hydrolytic conditions. 

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... 

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... 

Xylo-oligosaccharides. Samples of X4 through X7 of 98% purity or better and of X3 and X9 of 90% or better were prepared by acidic hydrolysis of larchwood xylan and preparative chromatography, as previously described (i). 

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

Table III. Possible Structure of Oligosaccharides Obtained by the Partial Acid Hydrolysis of Rice Bran Arabinogalactoglucuronoxylan...

To investigate this possibility, chitin oligosaccharides were first prepared by acid hydrolysis of chitin and separation of the products by HPLC... 

Fig. 4.5.6 Lipid-linked oligosaccharides (LLO) isolated from different CDG-I patients. Fibroblasts from a control and different CDG-I patients (CDG-lc, CDG-ld, CDG-lg, CDG-li) were metabolically labelled with 2-[3H]mannose for 30 min. [3H]oligosaccharides were released from LLO by mild acid hydrolysis and size-fractionated by HPLC. M5, M7, M9 and G3 refer to the positions of GlcNAc2Man5, GlcNAc2Man7, GlcNAc2Man9 and GlcNAc2Man9Glc3, respectively. The arrow marks shortened [2-3H]mannose-labelled oligosaccharides accumulating in the case of very early CDG-I types like CDG-li, which are often hard to detect by standard LLO-HPLC analysis...

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