Frank Lindh

Isolation of monosialylated oligosaccharides from human milk and structural analysis of three new compounds

The monosialyated oligosaccharide fraction from combined samples of human milk was fractionated by gel filtration, ion-exchange chromatography, and h.p.l.c. with triethylamine as an ion-pairing reagent. Among the twelve oligosaccharides isolated, three were new compounds for which the following structures were established on the basis of chemical analyses, f.a.b.-m.s., and n.m.r. spectroscopy.

Structural analysis of five new monosialylated oligosaccharides from human milk

The total monosialylated oligosaccharide fraction from pooled human milk was isolated by gel filtration and ion-exchange chromatography. Further separation by HPLC using a mobile phase containing an ion-pairing reagent of triethylamine gave five new monosialylated oligosaccharides. Structural analysis was carried out by chemical analyses, fast atom bombardment mass spectrometry, and 500-MHz NMR spectroscopy. Combined structural data revealed the following new structures: [formula: see text]

Structural studies of the O-specific side-chain of the lipopolysaccharide from Escherichia coli O 55

The structure of the O-specific side-chains of the lipopolysaccharide from Escherichia coli O 55 has been investigated, methylation analysis, specific degradations, and n.m.r. spectroscopy being the principal methods used. It is concluded that the O-specific side-chains are composed of pentasaccharide repeating-units having the following structure [where Col stands for colitose (3,6-dideoxy-L-xylo-hexose)].(See formula in text).

Structural studies of the capsular polysaccharide of Klebsiella type 33.

The capsular polysaccharide from Klebsiella type 28 has been studied by methylation analysis, a modified Smith-degradation procedure, and uronic acid degradation with subsequent oxidation and elimination of the substituents of the oxidized residue. The polysaccharide contained the hexasaccharide repeating-unit shown below. The terminal D-glucopyranose residue was hydrolysed by emulsin, indicating a beta linkage. The anomeric natures of other glycosidic linkages were determined by characterization of fragments obtained during the degradative studies. The D-galactopyranose residue was not present in any fragment, but is assumed to be alpha-linked from optical-rotation considerations. (see article)

Isolation and structural analysis of three new disialylated oligosaccharides from human milk

Five disialylated oligosaccharides, of which three were new compounds, were isolated from pooled human milk. The isolation procedure included gel filtration and ion-exchange chromatography and the final purification was accomplished by HPLC using a mobile phase containing triethylamine as an ion-pairing reagent. Structural analysis was carried out by chemical analyses, fast atom bombardment mass spectrometry, and 500-MHz NMR spectroscopy. The following new structures were found: (formula; see text).

High-performance liquid chromatography of sialic acid-containing oligosaccharides and acidic monosaccharides

Many sialic acid-containing oligosaccharides and five acidic monosaccharides have been separated by high-performance anion-exchange chromatography using a Dionex AS6 ion-exchange column eluted with aqueous 50 mM NaOH plus 50-175 mM sodium acetate. Using a pulsed amperometric detector, as little as 50 pmol oligosaccharide can be detected. Many factors, such as the presence of fucosyl groups or sialyl groups, glycosidic linkage positions, and branching structure, can have a tremendous influence on overall acidity of the oligosaccharide, which can lead to excellent separations and make this method an important addition to existing alternatives for the separation of sialic acid-containing oligosaccharides.

Determination of binding positions in oligosaccharides and glycosphingolipids by fast-atom-bombardment mass spectrometry

Application of f.a.b.-m.s. to the products obtained from glycoconjugates upon periodate oxidation followed by borohydride reduction and methylation gives the positions of binding of the monosaccharide residues on the basis of the sequences of the primary and secondary ions.

4-O-α-d-galactopyranosyl-d-galactose: Efficient synthetic routes from “polygalacturonic acid”

Abstract Enzymic hydrolysis of “polygalacturonic acid” gave a mixture of oligomers which was fractionated by ion-exchange chromatography. The resulting di- and tri-saccharides were treated, respectively, with methanol and ethylene oxide, and the resulting esters were reduced with sodium borohydride. Treatment of the products with acetic anhydride and sulfuric acid, followed by deacetylation, produced the title compound.

Structural studies of the capsular polysaccharide of Klebsiella type 30.

The structure of the capsular polysaccharide from Klebsiella type 33 has been investigated. Methylation analysis, various specific degradations, graded hydrolysis with acid, and n.m.r. spectroscopy were the principal methods used. It is concluded that the polysaccharide is composed of pentasaccharide repeating-units having the following structure. (formula, see manual). The D-galactopyranosyl group, with pyruvic acid linked as a ketal to O-3 AND O-4, was degraded on treatment of the fully methylated polysaccharide with strong base. It is proposed that methyl pyruvate is eliminated, in an E2 type of reaction.

A 1H and 13C NMR study of oligosaccharides from human milk. Application of the computer program CASPER

Several oligosaccharides from human milk, containing vicinally branched residues, have been analysed with respect to induced NMR chemical shift changes that originate from the branching. Two types of branching were investigated: (i) linear oligosaccharides with a 2-linked residue, which thus becomes vicinally 1,2-disubstituted, and (ii) oligosaccharides with either 2,3- or 3,4-branching. It could be concluded that, in 13C NMR spectra of the first type, for which only moderately sized induced changes (< 2 ppm) had been observed previously, large (> 5 ppm) changes are also present. For 2,3- and 3,4-branching, changes similar to those observed earlier were found. In 1H NMR spectra, significant induced shifts for signals from anomeric, aglyconic, and H-5 protons were observed. For most trisaccharides, a unique set of values for the chemical shift differences was found, thus making it suitable to use them for characterisation of substitution patterns in the analysis with the computer program CASPER.