High-resolution gas chromatographic separation of alditol acetates on fused-silica wall-coated open-tubular columns

Characterization of a strictly specific acid beta-galactosidase from Achatina achatina

An acid beta-galactosidase was isolated from the digestive juice of Achatina achatina and purified to homogeneity by anion exchange, gel-filtration and hydroxyapatite chromatographies. This enzyme is soluble, as are the cytosolic beta-galactosidases, functions at acid pH like the lysosomal enzymes but differs from the other soluble animal beta-galactosidases in that it is highly specific for the beta-D-galactosyl residue. In addition, it cleaves the beta1-4 linkage much faster than the beta1-3 and beta1-6 linkages. The enzyme is a monomeric glycoprotein with a molecular mass of 120-125 kDa and the carbohydrate moiety makes up approximately 6% (w/w) of the protein. The amino acid composition displays an important amount of acidic/amide and hydroxy amino acid residues and a low content of basic residues. The enzyme activity is markedly affected by the ionic strength of the medium and the rate-pH curve was shifted towards higher pH values in the presence of added salt. Acid beta-galactosidase is capable of catalysing transgalactosylation reactions. The yields of galactosylation of hydroxy amino acid derivatives, catalysed by the enzyme in the presence of lactose as the glycosyl donor, were higher than those reported previously with conventional sources of beta-galactosidases. In addition, the pH optimum is different for the hydrolysis (pH 3.2) and transgalactosylation (pH 5.0) reactions. On the basis of this work, the enzyme could be used as a tool in the structural analysis of D-galactose-containing oligosaccharide chains, as well as for the synthesis of glycoconjugates.

Capillary gas-chromatographic analysis of monosaccharides: improvements and comparisons using trifluoroacetylation and trimethylsilylation of sugar O-benzyl- and O-methyl-oximes

Two new procedures for the gas-chromatographic analysis of monosaccharides are reported. One involves derivatization of the sugars by reaction with O-benzylhydroxylamine followed by trifluoroacetylation with N-methylbis(trifluoroacetamide) and chromatography on a DB-1701 capillary column. This technique probably provides the best resolution achieved to date of the C3-C6 aldoses, as well as of the corresponding alditols. Ketoses can be qualitatively analyzed by this method, but complications interfere with their quantitative analysis. The second procedure also involves initial derivatization as the O-benzyloxime, but is followed by trimethylsilylation with 1-trimethylsilylimidazole, and chromatography on a DB-17 column. This technique is particularly useful for C5 sugars, C6 ketoses, and mixtures of sugars, alditols, and/or lactones. A number of additional, critical, observations on the derivatization and capillary gas-chromatographic analysis of monosaccharides are described.

Determination of the carbohydrate composition of mammalian glycoproteins by capillary gas chromatography/mass spectrometry

A technique to determine the carbohydrate composition of glycoproteins using capillary gas chromatography/mass spectrometry (electron impact) with selected ion monitoring is described. This method entails hydrolysis with methanolic-HCl followed by formation of trimethylsilyl methylglycoside derivatives, extraction of the carbohydrate derivatives into hexane, and GC/MS analysis. For those carbohydrates that are present in animal glycoproteins including fucose, mannose, galactose, glucosamine, galactosamine, and N-acetylneuraminic acid (sialic acid), the sensitivity of this assay was approximately 1-3 pmol and the assay was linear over a 100-fold range. The carbohydrate compositions determined on small quantities (1-10 pmol) of various glycoproteins including human transferrin and alpha-1 acid glycoprotein, fetuin, and ovalbumin were identical to their reported carbohydrate content and compositions. Major advantages of this technique include the time required to complete the sample preparation and analysis (less than 8 h), the sensitivity and specificity of the assay, and the fact that all carbohydrate moieties, including sialic acid, can be quantitated in a single hydrolysate of a glycoprotein.

A quantitative determination by capillary gas-liquid chromatography of neutral and amino sugars (as O-methyloxime acetates), and a study on hydrolytic conditions for glycoproteins and polysaccharides in order to increase sugar recoveries

Complete gas-liquid chromatographic separation of O-methyloxime acetates (syn and anti isomers) prepared from eight neutral sugars, three hexosamines, and muramic acid has been obtained, using a fused-silica Carbowax 20M capillary column. A single hydrolytic step for carbohydrate-containing biological material (less than or equal to 2.5 X 10(-3) M sugar solution in 4 N trifluoroacetic acid at 125 degrees C for 1 h) has been developed, and results have been compared with those obtained with standard hydrolytic conditions in order to ensure complete release of amino sugars from glycoproteins, together with minimum losses of neutral sugars. The combination of this acid hydrolysis with the above improved derivatization procedure for the gas-liquid chromatographic analysis has led to a simple, rapid, and sensitive analytical method, which has been successfully tested on three glycoproteins (fetuin, mucin, and peroxidase) and two plant cell-wall polysaccharide fractions (soluble fibers from carrots and soybeans).

Capillary gas chromatographic analysis of alditol acetates of neutral and amino sugars in bacterial cell walls

Several improvements in the preparation of alditol acetates of neutral and amino sugars and in the preparation of glass capillary columns for their separation are described. Modifications in sample preparation permitted the simultaneous processing of multiple samples and eliminated extraneous background peaks. Efficient and inert columns were tailor-made for the separation of alditol acetates of neutral and amino sugars by leaching glass capillaries with aqueous hydrochloric acid and dynamically coating with SP-2330.