Authentic standards for the reductive-cleavage method: the positional isomers of partially methylated and acetylated or benzoylated 1,5-anhydro-L-arabinitol

Described herein is the synthesis of the eight positional isomers of methylated and acetylated or benzoylated 1,5-anhydro-L-arabinitol. The compounds were generated simultaneously from 1,5-anhydro-L-arabinitol by sequential partial methylation and benzoylation and isolated in pure from by high-performance liquid chromatography. The desired acetates were obtained by debenzoylation and acetylation of the pure isomers. Reported herein are the 1H NMR spectra of the benzoates and the electron-ionization mass spectra of the acetates and the tri-O-methyl derivative. Also reported for the acetates and the tri-O-methyl derivative are their linear temperature-programmed gas-liquid chromatography retention indices on three different capillary columns.

Separation of alditols of interest in food products by high-performance anion-exchange chromatography with pulsed amperometric detection

High-performance anion-exchange chromatography (HPAEC)-pulsed amperometric detection (PAD) employing a CarboPac MA 1 column was investigated with respect to mobile phase composition, linear response characteristics, repeatability, reproducibility and sensitivity with different alditols used as sugar substitutes in food and confectionery products. The energy-reduced bulk sweeteners isomalt and maltitol were well resolved in less than 25 min by isocratic elution with 600 mM sodium hydroxide solution. HPAEC-PAD was also successfully applied to the determination of alditols in sugar-free products and a low-calorie sweetener containing sorbitol, mannitol and fructose at different levels.

O-glycosylated species of natural human tumor-necrosis factor-alpha

Tumor-necrosis factor-alpha, produced by human B-cell lymphoblastoid cell line BALL-1, was expressed as four protein bands on SDS/PAGE analysis. It may have been glycosylated, based on the fact that the heavier two of the four bands disappeared after neuraminidase treatment. Sugar composition analyses revealed that the tumor necrosis factor-alpha contained galactose, N-acetylgalactosamine and N-acetylneuraminic acid as sugar components. To prepare sugar chains, tumor necrosis factor-alpha was treated with alkaline borodeuteride and the oligosaccharide-alditols liberated were fractionated by gel-filtration chromatography on a Bio-Gel P-4 column, followed by normal-phase HPLC. Three oligosaccharide-alditols were obtained, and the structures of two of them were identified by methylation analysis and exoglycosidase digestion. The structures of these oligosaccharide-alditols were Gal beta 1-3(NeuAc alpha 2-6)GalNAcol and Gal beta 1-3GalNAcol (GalNAcol, N-acetylgalactosaminitol). The structure of the remaining oligosaccharide-alditol was determined to be NeuAc alpha 2-3Gal1-3GalNAcol by composition and methylation analyses. About 20% of tumor necrosis factor-alpha was found to be 0-glycosylated, based on the results of the sugar composition and structure analyses. An amino acid sequence analysis of the glycosylated peptides was performed after Staphylococcus aureus V8 protease digestion of tumor necrosis factor-alpha had been completed, and it was proved that the 0-glycosylation site of tumor necrosis factor-alpha was Ser 4.

Structure of four acidic oligosaccharides from the jelly coat surrounding the eggs of Xenopus laevis

Novel acidic oligosaccharides were released by reductive beta-elimination from the jelly coat eggs of the Anuran Xenopus laevis. According to the structural analysis of these oligosaccharide-alditols, the following structures are proposed: [sequence: see text] where Kdn, 3-deoxy-D-glycero-D-galactononulosonic acid. These results confirm the species specificity of the glycanic structures present in the secretion of amphibian oviducts, and may form the basis of a specific egg-sperm recognition process.

Structure of six 3-deoxy-D-glycero-D-galacto-nonulosonic acid(Kdn)-containing oligosaccharide-alditols released from oviduct secretions of Ambystoma maculatum. Characterization of the sequence fucosyl(alpha 1-2)[fucosyl(alpha 1-3)]fucosyl(alpha 1-4)-3-deoxy-D-glycero-D-galacto-nonulosonic acid

The O-linked acidic oligosaccharides of the jelly coat surrounding the eggs of Ambystoma maculatum were analyzed by NMR spectroscopy. The structures of the major oligosaccharides were established as follows where Kdn represents 3-deoxy-D-glycero-D-galacto-nonulsonic acid and GalNAc-ol is N-acetylgalactosaminitol: [sequence: see text] As shown for five other amphibian species, the structures of these carbohydrate chains appear to be species specific and can afford a basis for molecular taxonomy. These new sequences also reflect the occurrence of specific fucosyltransferase activities that are characteristic of Ambystoma maculatum.

Structural studies on the hexasaccharide alditols isolated from the carbohydrate-protein linkage region of dermatan sulfate proteoglycans of bovine aorta. Demonstration of iduronic acid-containing components

Five major hexasaccharide alditols were isolated from the carbohydrate-protein linkage region of bovine aorta dermatan sulfate peptidoglycans after reductive beta-elimination and subsequent chondroitinase ABC digestion. These molecules account for at least 55.3% of the total linkage region. Their structures were analyzed by enzymatic digestion in conjunction with high performance liquid chromatography, electrospray ionization mass spectrometry, and 500-MHz one- and two-dimensional 1H NMR spectroscopy. Three of these compounds have the conventional hexasaccharide core; delta HexA alpha 1-3Gal-NAc beta 1-4GlcA beta 1-3Gal beta 1-3Gal beta 1-4Xyl-ol. One is nonsulfated, and the other two are monosulfated on C6 or C4 of the GalNAc residue. They represent at least 6.3, 5.2, and 28.8% of the total linkage region, respectively. The other two compounds have the following hitherto unreported hexasaccharide core with an internal iduronic acid residue in common; delta HexA alpha 1-3GalNAc beta 1-4IdoA alpha 1-3Gal beta 1-3Gal beta 1-4Xyl-ol. One is monosulfated on C4 of the GalNAc, and the other is disulfated on C4 of the GalNAc and of the galactose residue substituted by the iduronic acid residue. These two compounds account for 35% of the five isolated hexasaccharide alditols and at least 4.3 and 10.7% of the total linkage region, respectively. The latter two structures form a striking contrast to the currently accepted conception that heparin, heparan sulfate, and chondroitin/dermatan sulfate share the common linkage tetrasaccharide core GlcA beta 1-3Gal beta 1-3Gal beta 1-4Xyl. The biological significance of the isolated structures is discussed in relation to the biological functions and the biosynthetic mechanisms of dermatan sulfate.

Isolation and characterization of natural protein-associated carbohydrate ligands for E-selectin

A comparative analysis of carbohydrate 'libraries' derived from cell lines binding E-selectin with differing avidity identified endogenous protein-associated carbohydrate ligand candidates for E-selectin. Three unusual structures, which constitute less than 3% of cell surface protein-associated carbohydrate, were unique to the E-selectin-binding cells, including neutrophils and the monocytic cell line U937. All are tetraantennary N-linked structures with a NeuAc alpha 2-->3Gal beta 1-->4(Fuc alpha 1-->3)GlcNAc beta 1-->3Gal beta 1-->4- (Fuc alpha 1-->3)GlcNAc lactosaminoglycan extension (diSLex) on the arm linked through the C4 residue on the mannose. While all contained the expected SLex [NeuAc alpha 2-->3Gal beta 1-->4(Fuc alpha 1-->3)GlcNAc] moiety, these structures have an additional fucosylated lactosamine unit. Direct evidence that these diSLex-containing structures are, indeed, high-affinity ligands for E-selectin came from the use of recombinant soluble E-selectin-agarose affinity chromatography. We found that these three carbohydrate structures bound specifically to the E-selectin column. SLex itself does not bind under identical conditions. In summary, these related structures: (1) all possess an unusual 3-sialyl di-Lewis x extension on one arm of an N-linked tetraantennary glycan; (2) of the cells tested, are present only on E-selectin-binding leukocytes and leukocytic cell lines; (3) bind to E-selectin with a relatively high affinity (Kd < microM) and one greater than that of 3-sialyl Lewis x or 3-sialyl Lewis a; and (4) represent a very small percentage of the protein-associated carbohydrate. These carbohydrate structures appear to be present on only a very small number of cell surface proteins and may alone be responsible for the specificity of E-selectin-dependent adhesion.

Structure of the major neutral oligosaccharide-alditols released from the egg jelly coats of Axolotl maculatum. Characterization of the carbohydrate sequence GalNAc(beta 1-4)[Fuc(alpha 1-3)] GlcNAc(beta 1-3/6)

Several O-linked oligosaccharides of the jelly coat surrounding the eggs of Axolotl maculatum were analysed by 1H-NMR spectroscopy. The four major oligosaccharidealditols released by reductive beta-elimination display either the Lewisx (Lex) determinant or the sequence GalNAc(beta 1-4)[Fuc(alpha 1-3)]GlcNAc. This last structure has previously been characterized in allergenically active oligosaccharides isolated from the sea squirt H-antigen, and in the N-linked glycans of Schistosoma mansoni and human urokinase. It represents the major carbohydrate chain found in A. maculatum, the oviduct of which constitutes an excellent source of beta 1-4-acetylgalactosaminyl transferase activity. Moreover, the carbohydrate chains isolated from A. maculatum are quite different from those found in seven other amphibian species, in which the presence of species-specific material has been characterized. The role of carbohydrates appears more and more apparent during the fertilization process, and the diversity of the O-linked oligosaccharides supports such a biological role.

Separation of neutral oligosaccharide alditols from human meconium using high-pH anion-exchange chromatography

Neutral reduced oligosaccharides are in general not sufficiently retained to achieve adequate separation and reproducible chromatography using high-pH anion-exchange chromatography. We describe a method to increase the retention using two columns in series. This method has been applied to the separation of oligosaccharides purified from human meconium glycoproteins, obtained as their alditols after alkaline-borohydride release of oligosaccharides. The neutral oligosaccharide alditols were significantly retained upon two CarboPac PA-100 columns, connected in series, and eluted in 80 mM sodium hydroxide between 4 and 10 min. Three sialylated alditols studied were substantially retained and could be eluted in a gradient of 0-500 mM sodium acetate-80 mM sodium hydroxide between 10 and 45 min. The elution patterns were based on their size, charge and linkage, such that oligosaccharide alditol isomers could be separated.

Use of a porous graphitised carbon column for the high-performance liquid chromatography of oligosaccharides, alditols and glycopeptides with subsequent mass spectrometry analysis

HPLC using a porous graphitised carbon (PGC) column eluted in acetonitrile-aqueous trifluoroacetic acid has been shown to give complementary chromatography to reversed-phase (ODS) HPLC for separation of peptides and glycopeptides. The PGC column can also be used for separation of oligosaccharides and oligosaccharide alditols released from protein by enzymes (N-linked chains) or base-borohydride degradation (O-linked chains). The advantages are that peptides, glycopeptides, reducing oligosaccharides, sialylated oligosaccharides and oligosaccharide alditols can be chromatographed under the same conditions. The samples can be readily recovered by evaporation for sensitive liquid secondary ion mass spectrometric (LSI-MS) analysis and there is no contamination or deterioration of chromatography from column leakage. LSI-MS analysis revealed that complete peak separation of all of the possible oligosaccharide components of the standard glycoproteins fetuin and bovine submaxillary mucin was not achieved. However, PGC remains as a useful adjunct to other HPLC profiling and separation techniques in particular where subsequent MS analysis is desired.

Isolation and structural characterization of novel sialylated oligosaccharide-alditols from respiratory-mucus glycoproteins of a patient suffering from bronchiectasis

The carbohydrate chains of the respiratory-mucus glycoproteins of a patient (blood group O) suffering from bronchiectasis due to Kartagener's syndrome, were released by alkaline borohydride treatment of a pronase digest. The structures of 82 neutral and low-molecular-mass sialylated oligosaccharides have been described previously [van Kuik A., de Waard P., Vliegenthart J. F. G., Klein A., Carnoy C., Lamblin G. Roussel P. (1991) Eur. J. Biochem. 198, 169-182]. In the present work, medium-size sialylated oligosaccharides were obtained after ion-exchange chromatography and were subsequently separated into 36 fractions utilizing gel filtration, HPLC on normal-phase alkylamine-bonded silica and reverse-phase HPLC. From these fractions, the following six sialylated hepta- and octa-saccharide-alditols have been characterized by employing 500-MHz 1H-NMR spectroscopy, in conjunction with fast-atom-bombardment mass spectroscopy and methylation analysis. [formula: see text]

Separation of mucin oligosaccharide-alditols by high performance liquid chromatography on alkylamine-bonded silica columns. Effects of structural parameters

Forty five oligosaccharide-alditols, purified after reductive beta-elimination of human bronchial mucins, were analyzed by HPLC on alkylamine-bonded silica column (Lichrosorb-NH2). The comparison of their structural features and retention times permitted the extension of some previous findings. The chromatographic behavior of the oligosaccharide depends more on the accessibility of oligosaccharide hydroxyl groups than on the sugar composition. The use of this type of fractionation is very efficient for low-molecular-mass oligosaccharide-alditols but needs to be completed by a second chromatographic step for higher molecular-mass oligosaccharide-alditols.

Determination of monosaccharides and sugar alcohols in tissues from diabetic rats by high-performance liquid chromatography with pulsed amperometric detection

A sensitive and simple high-performance liquid chromatographic method has been developed to determine the concentration of monosaccharides and sugar alcohols in animal tissues. Five neutral monosaccharides (D-glucose, D-galactose, D-mannose, D-fructose, and D-ribose) and three neutral sugar alcohols (myo-inositol, glycerol, and D-sorbitol) predominate in the renal cortices and sciatic nerves of rats. These monosaccharides and sugar alcohols were extracted with distilled water, purified by deproteinization with ethanol, a Sep-Pak C18 cartridge, and columns of Dowex 50W-X8 and Amberlite CG-400, then separated on Ca2+ and Pb2+ cation-exchange columns, eluted with deionized distilled water at 80 degrees C, and detected using integrated pulsed amperometry. About 10 pmol of each sugar was detectable with a signal-to-noise ratio of 10:1. D-Glucose, D-fructose, D-sorbitol, and D-mannose were higher in both the renal and sciatic tissues of diabetic rats than in those of normal animals. D-Ribose and glycerol were higher in the renal cortex of diabetic animals.

High-performance liquid chromatography of oligosaccharide alditols and glycopeptides on a graphitized carbon column

The chromatographic behaviour of oligosaccharide alditols and glycopeptides containing neutral and acetamido sugars and sialic acid has been investigated on a HyperCarb porous graphitised carbon column. The alditols were substantially retained and could be eluted in 0-25% acetonitrile-0.05% trifluoroacetic acid in 0.05% aqueous trifluoroacetic acid between 3-30 min for mono- to hexasaccharides. Elution patterns were based on both size, charge and linkage such that isomeric compounds could be separated from each other.

The broad diversity of neutral and sialylated oligosaccharides derived from human salivary mucins

Mucin glycopeptides were prepared from the salivary mucins of 20 healthy donors with blood group O. The carbohydrate chains of the high-molecular-weight mucins were released by alkaline borohydride treatment. Neutral and monosialylated oligosaccharide-alditols were purified by ion-exchange chromatography, gel filtration, and HPLC. The structures of the oligosaccharide-alditols were determined by high-resolution 1H-NMR spectroscopy in combination with fast atom bombardment mass spectrometry and methylation analysis. Thirty-seven oligosaccharide-alditols were characterized and illustrate the extreme diversity of the salivary mucins carbohydrate chains. This diversity might represent a mosaic of bacterial adhesion sites and be involved in the early events of the nonimmune defense of the oral cavity. Among these 37 oligosaccharide-alditols, 31 have not been previously described in human saliva and five of these are novel structures: [formula: see text]

A comprehensive procedure for preparation of partially methylated alditol acetates from glycoprotein carbohydrates

Various steps involved in the preparation of partially methylated alditol acetates (PMAAs) from glycoprotein-derived carbohydrates were improved to obtain the derivatives in a rapid manner with excellent yields. Carbohydrates were permethylated in dimethyl sulfoxide (DMSO), using a fine suspension of sodium hydroxide and methyl iodide (CH3I). The fine suspension of NaOH was prepared conveniently from commercially available 50% aqueous NaOH in DMSO by sonication and washing the precipitate with DMSO. Methylation of ovalbumin and fetuin glycopeptides using the fine suspension of NaOH and CH3I was complete within 5 min, and the methylation reaction did not generate any nonsugar artifacts. Methylated carbohydrates without any purification were hydrolyzed in a mixture of volatile organic acids, which permitted rapid removal of the acids from samples by evaporation. Acetylation of partially methylated alditols with acetic anhydride for 2-4 h at ambient temperature using 4-N,N'-dimethylaminopyridine as a catalyst and the reaction was free from generating nonsugar reaction artifacts. The reaction time course for methylation, hydrolysis, and acetylation was determined to obtain optimum reaction conditions for preparation of the PMAAs. The procedure facilitated rapid identification and quantitation of PMAAs due to diminished reaction artifacts and the quality of the chromatogram depended only on the purity of starting material and the reagents used for the methylation analysis. Utility of these simple methods for rapid methylation analysis was demonstrated in the characterization of oligosaccharides isolated in small amounts using a carbohydrate analyzer.

Structure of an allergenic pentasaccharitol, Gp-1 beta-b6, isolated from a sea squirt antigen, Gi-rep, as a minimum structural unit responsible for its allergenicity

An allergenic pentasaccharitol, Gp-1 beta-b6, was isolated as a minimum structural unit responsible for the allergic reaction in skin of patients with sea squirt allergy from a saccharitol fraction, Gp-1 beta-b, that had been liberated by beta-elimination from a glycopeptide in a Pronase digest of a sea squirt antigen, Gi-rep. Methylation/GC-MS and FAB-MS analyses indicated the sugar sequence of Gp-1 beta-b6 to be GalNAcl----2Fucl----(GalNAc1----) 3,4GlcNAc1----3GalNAc-ol. To analyze the structure in more detail, Gp-1 beta-b6 was labeled with p-aminobenzoic acid ethyl ester (ABEE), i.e., the reducing terminal 3-O-substituted GalNAc-ol of the saccharitol was oxidized to 2-O-substituted L-ThrNAc with equimolar periodate, and the resultant aldehyde was labeled with ABEE by reductive amination. The ABEE-labeled Gp-1 beta-b6 was subjected to sequential exoglycosidase digestion with beta-N-acetylhexosaminidase, alpha-N-acetylgalactosaminidase, and alpha-fucosidase, and the digests were chromatographed on an HPLC column of TSK gel Amide 80. From the results of the HPLC, methylation/GC-MS, and FAB-MS analyses of the digests of the labeled substrate, the structure of Gp-1 beta-b6 was determined to be GalNAc alpha 1----2Fuc alpha 1----3(GalNAc beta 1----4)GlcNAc beta 1----3GalNAc-ol. Enzymatic elimination of either the non-reducing terminal beta-GalNAc or the non-reducing terminal alpha-GalNAc led to inactivation of the allergenic pentasaccharitol. Accordingly, it is possible that the allergenic saccharitol contains two disaccharide units as the allergy-specific epitopes, one GalNAc alpha 1----2Fuc alpha 1---- and the other GlcNAc beta 1----4GLcNAc beta 1----.

Thin-layer electrophoretic separation of monosaccharides, oligosaccharides and related compounds on reverse phase silica gel

The electrophoretic mobilities of monosaccharides, oligosaccharides, sugar alcohols and sugar acids were determined in 0.3 M borate buffer, pH 10, using thin-layer electrophoresis on silanized silica gel, pretreated with octanol-1. A rapid separation of a number of sugars, occurring in foods, could be achieved. Using a 0.05-0.1 M neutral solution of barium acetate as electrolyte, thin-layer electrophoresis allowed excellent and rapid separation as well as identification of all common uronic acids which are constituents of many acidic polysaccharides.

Sugar sequences of allergenically active oligosaccharide alcohols isolated from a large-molecular-size sea squirt antigen termed H-antigen

O-Glycosidically linked oligosaccharide chains were liberated as oligosaccharide alcohols (HPG-beta 2) by beta-elimination treatment from a glycopeptide fraction (HPG, Mr ca. 10(5)) that was isolated from a Pronase digest of a large-size sea squirt antigen termed H-antigen (Mr 10(6)-2 X 10(7)). After HPG-beta 2 was divided into a neutral (HPG-beta 2-N) and an acidic (HPG-beta 2-A) fraction, 11 neutral saccharitols were isolated from HPG-beta 2-N, and their sugar sequences were determined by methylation/GC-MS, FAB-MS, and/or DI/EI-MS. By skin tests specific to patients with sea squirt allergy, it was found that six saccharitols were allergenically active but five were inactive. Furthermore, active saccharitols were all of branched structure containing two nonreducing terminal GalNAc (t-GalNAc) residues, whereas the inactive saccharitols contained one or no t-GalNAc. Since the allergic reaction in skin should depend on the crosslinking of IgE antibodies by certain allergens carrying two or more epitopes, three types of N-acetylgalactosaminyl disaccharide units, GalNAc1----2Fuc1----, GalNAc1----3/4GalNAc1----, and GalNAc1----3/4GlcNAc1----, were nominated as the major components of the allergy-specific epitopes in the active saccharitols. Such multiplicity of the epitope structures might reflect the polyclonality of the specific IgE antibodies.

Isolation and structural characterization of low-molecular-mass monosialyl oligosaccharides derived from respiratory-mucus glycoproteins of a patient suffering from bronchiectasis

The carbohydrate chains of the respiratory-mucus glycoproteins of a patient suffering from bronchiectasis due to Kartagener's syndrome were released by alkaline borohydride treatment. Low-molecular-mass, monosialyl oligosaccharide-alditols were isolated by anion-exchange chromatography and fractionated by consecutive straight-phase high-performance liquid chromatography (HPLC) on a silica-based alkylamine column, and reverse-phase HPLC on a silica-based octadecyl column, respectively. The structures of the oligosaccharidealditols were determined by 500-MHz 1H-NMR spectroscopy in combination with sugar composition analysis. The 24 structures established range in size from disaccharides to heptasaccharides. Novel oligosaccharides obtained from the bronchiectasis mucus glycoproteins are: (formula; see text) 23 of the 24 monosialyl oligosaccharides characterized can be conceived of as extensions of neutral oligosaccharides purified from the bronchial mucus of this patient [Klein, A. et al. (1988) Eur. J. Biochem. 171, 631-642; Breg, J. et al. (1988) Eur. J Biochem. 171, 643-654]. The sialic acid residue was found to occur either in alpha (2----3)- or alpha (2----6)-linkage to a galactosyl residue or in alpha (2----6)-linkage to GalNAc-ol.

Structural elucidation of glycosaminoglycans through characterization of disaccharides obtained after fragmentation by hydrazine-nitrous acid treatment

Hydrazinolysis of glycosaminoglycans to bring about N-deacetylation followed by nitrous acid treatment to effect deaminative cleavage at alternating hexosamine residues has been used to make possible identification and quantitation of disaccharide sequences and position of O-sulfate substitution in nanogram amounts of these polymers. After radiolabeling by NaB3H4 reduction the hydrazine-nitrous acid products were fractionated on Dowex 1 and further resolved by thin-layer chromatography into disaccharides terminating in either sulfated or unsulfated anhydromannitol or anhydrotalitol. Fragmentation of hyaluronic acid, keratan sulfate, chondroitin 4-sulfate, chondroitin 6-sulfate, dermatan sulfate, and heparin yielded a total of 14 disaccharides comprising the major sequences (greater than 1 mol%) occurring in mammalian glycosaminoglycans. Disaccharides representing the predominant variants of the chondroitin sulfates [GlcUA beta 1----3anhydrotalitol(4-SO4) and GlcUA beta 1----3anhydrotalitol(6-SO4)] as well as of dermatan sulfate chains [IdUA alpha 1----3anhydrotalitol(4-SO4) and GlcUA beta 1----3anhydrotalitol(4-SO4)] chains could readily be quantitated by this approach. In the case of heparin a comparison of the disaccharides produced by direct nitrous acid and hydrazine-nitrous acid treatments moreover provided an assessment of the distribution of N-sulfate groups. The characterization of the various disaccharides by Smith periodic acid degradation and glycosidase digestions was facilitated by the preparation and thin-layer chromatographic resolution of the complete series of monosulfated derivatives of anhydromannitol and anhydrotalitol; the sulfate esters were shown to be stable to both the hydrazine and nitrous acid treatments. The high sensitivity of the hydrazine-nitrous acid fragmentation procedure should prove useful in the structural elucidation of cell surface and basement membrane proteoglycans as well as other sulfated glycoconjugates which are present in small amounts.