Separation of sialyl-oligosaccharides by high-performance liquid chromatography. Application to analysis of carbohydrate units of acidic oligosaccharides obtained by hydrazinolysis of hen ovomucoid

Comparative study of asparagine-linked glycans of plasma T-kininogen in normal rats and during acute inflammation

Rat T-kininogen has been separated into two molecular variants by affinity chromatography on concanavalin A (ConA): a ConA-reactive (ConA+) and a ConA-non-reactive (ConA-) fraction, from which carbohydrate chains were quantitatively released by hydrazinolysis. On the basis of high-resolution 400 MHz 1H-n.m.r. spectroscopy of the re-N-acetylated hydrazinolysates, the carbohydrate structures of the two ConA molecular variants of rat T-kininogen were established. The ConA-non-reactive species contains a single type of carbohydrate chain with the following structure: [formula: see text] The ConA-reactive fraction contains the same structure and the following additional one: [formula: see text] The relative abundance of the two molecular forms is profoundly affected during inflammation (ratio ConA+/ConA-: 44% in normal and 95% in inflamed T-kininogen), but no structural modification of the carbohydrate chains was observed.

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.

Carbohydrate analysis of glycoproteins. A review

Many of the products prepared by biotechnological approaches, including recombinant genetic engineering, cell tissue culture, and monoclonal technologies, are glycoproteins. As little as five years ago, glycosylation was believed to play no significant role in the function of glycoproteins. Recent large scale testing of glycoprotein-based pharmaceuticals has indicated that both the extent and type of glycosylation can play a central role in glycoprotein activity. Although methods for compositional and sequence analysis of proteins and nucleic acids are generally available, similar methods have yet to be developed for carbohydrate oligomers and polymers. This review focuses on new, developing methods for the analysis and sequencing of the carbohydrate portion of glycoproteins. Included are: (1) the release of oligosaccharides and hydrolysis of carbohydrate chains using enzymatic and chemical methods; (2) fractionation by LPLC, electrophoresis, HPLC, and lectin affinity chromatography; (3) detection through the preparation of derivatives or by new electrochemical methods; (4) analysis by spectroscopic methods, including MS and high-field NMR; and (5) their sequencing through the use of multiple, well-integrated techniques. The ultimate goal of the analytical approaches discussed is to firmly establish structure and, thus, permit the study of structure-function relationships and eventually to allow the intelligent application of carbohydrate remodeling techniques in the preparation of new glycoproteins.

Primary structure of horse serotransferrin glycans. Demonstration that heterogeneity is related to the number of glycans and to the presence of N-acetylneuraminic acid and N-acetyl-4-O-acetylneuraminic acid

Three serotransferrin variants Tf 2a, Tf 4b and Tf 5b were isolated in an homogeneous form from a preparation of homozygous horse serotransferrin Tf 0. On the basis of the results concerning molecular mass determination and the carbohydrate analysis, it is concluded that the serotransferrin variant Tf 2a contains only one glycan while variants Tf 4b and Tf 5b contain two glycans. The structure of all of the glycans has been established by combining methylation analysis, mass spectrometry and 400-MHz 1H-NMR spectroscopy. From the obtained results, it appears that the two glycans of Tf 5b variant are, like in human serotransferrin, of the N-acetyllactosaminic biantennary type, fully sialylated by two residues of N-acetylneuraminic acid (Neu5Ac; glycan type I). In contrast, in addition to this structure, two N-acetyllactosaminic biantennary isomeric structures named type II-A and type II-B sialylated by one Neu5Ac residue and one N-acetyl-4-O-acetylneuraminic acid [Neu(4,5)Ac2] residue located either at Gal6 or 6' and one N-acetyllactosaminic biantennary structure (named type III) sialylated by two residues of Neu(4,5)Ac2, were identified in variants Tf 2a and Tf 4b. These results demonstrate that in an homozygous preparation of horse serotransferrin Tf 0, the heterogeneity is dependent, on the one hand, on the nature of the neuraminic acid substituting a N-acetyllactosaminic biantennary structure and, on the other hand, on the number of glycans bound to the polypeptide chain. Moreover, the differences which exist in the molecular mass of 77.5 kDA, 80 kDa and 82 kDa for serotransferrin variants Tf 2a, Tf 4b and Tf 5b, respectively, are not completely explained by the structure and the number of the glycans suggesting that the three variants should also differ in their polypeptide chain.

Size fractionation of oligosaccharides by liquid chromatography on a cation-exchange column

Oligosaccharides, labelled with 2-aminopyridine at their reducing ends, were satisfactorily fractionated according to the sugar sizes on Shodex RSpak DC-613, a cation-exchange resin column (Na+ form), with water-acetonitrile as the eluent in the presence of sodium acetate or triethylammonium acetate buffer. For the fractionation of sugar samples, dextran hydrolyzates, chitin oligomers and oligosaccharide moieties of ovomucoid were used. The oligosaccharides were strongly adsorbed to the resin column with solvents containing less water and at lower temperature, and were eluted in order of increasing molecular size above the critical concentration of acetonitrile. Baseline separation of a dextran hydrolyzate up to oligomers having 20 glucose units was observed by gradient elution. The separation efficiency and elution pattern were investigated by changing the buffer concentration, mobile phase pH and temperature.

Isolation of the major O-glycosidically linked oligosaccharides obtained by alkaline borohydride degradation of human meconium glycoproteins

Neutral and acidic oligosaccharides derived from human meconium glycoproteins by alkaline borohydride degradation have been separated by high-performance liquid chromatography on a Micro-Pak anion-exchange column. In each class, oligosaccharides were purified by normal-phase (neutral and acidic oligosaccharides) and reversed-phase (neutral oligosaccharides) chromatography. Effective separations of neutral oligosaccharides and acidic oligosaccharides were achieved.

Separation of sialyl-oligosaccharides by medium pressure anion-exchange chromatography on Mono Q

On columns prepacked with the recently introduced anion-exchange material, Mono Q (Pharmacia), sialyl-oligosaccharides could be fractionated excellently according to the sialic acid content. With u.v. absorption at 214 nm as the detection method, analytical runs of carbohydrate material on the microgram scale, were possible. The value of the method for preparative purposes was demonstrated for sialic acid-containing carbohydrates obtained from human serotransferrin by hydrazinolysis.

Separation of sialyl-oligosaccharides by high-performance liquid chromatography. Application to the analysis of mono-, di-, tri- and tetrasialyl-oligosaccharides obtained by hydrazinolysis of alpha 1-acid glycoprotein

High-performance liquid chromatography has been applied to the separation of isomers of mono-, di-, tri- and tetrasialylated oligosaccharides derived from alpha 1-acid glycoprotein by hydrazinolysis. The separation of the sialyl-oligosaccharides on the basis of their negative charges was carried out with quaternary amine-bonded silica. Within each class, the anionic oligosaccharides were fractionated on the basis of their net carbohydrate content on alkylamine-modified silica using a mobile phase consisting of a mixture of acetonitrile and potassium dihydrogen phosphate with 0.01% of 1,4-diaminobutane or 0.01% of tetraethylpentamine.