The Structure of the Carbohydrate Moiety of a Glycopeptide GP-I-b from Rhizopus Saccharogenic Amylase

The structure of the carbohydrate moiety of GP–I–b which is one out of three glycopeptides isolated from a Pronase digest of the saccharogenic amylase of Rhizopus javanicus sp. 3–46, was investigated by enzymatic and chemical techniques.

Nine moles of mannose followed by one mole of N-acetylglucosamine were released per mole of GP–I–b when it was treated sequentially with purified jack bean α-mannosidase and β-N-acetylglucosaminidase.

Methylation of GP–I–b gave 3, 6-di-O-methyl derivative from the N-acetylglucosamine residues, and 2, 3, 4, 6-tetra-O-methyl, 3, 4, 6-tri-O-methyl and 2, 4-di-O-methyl derivatives from the mannose residues in an approximate ratio of 3: 4: 2.

A smaller glycopeptide (F–l) containing two moles each of mannose and N-acetylglucosamine per mole of asparagine was obtained when GP–I–b was subjected to one step of the Smith degradation. Exhaustive methylation of F–l gave 3, 6-di-O-methyl derivative of Nacetylglucosamine, and 2, 3, 4, 6-tetra-O-methyl and 2, 3, 4-tri-O-methyl derivatives of mannose in a ratio of 1.00: 0.85.

Controlled acetolysis of GP–I–b yielded mannose, O-α-mannosyl-(l→2)-O-α-mannosyl-(l→3)-mannose and a smaller glycopeptide which was resistant to the acetolysis.

From these and previous evidences, the following structure was determined for GP–I–b.     

The Structure of the Carbohydrate Moietv of a Glycopeptide GP-I-a from Rhizopus Saccharogenic Amylase

The structure of the carbohydrate moiety of GP–I–a, one of three glycopeptides obtained from Rhizopus saccharogenic amylase, was determined by using enzymatic and chemical techniques.

Six residues (all of the residues in GP–I–a) of mannose and one residue of N-acetylglucosamine were released in that order when GP–I–a was digested successively with purified α-mannosidase and β-N-acetylglucosaminidase.

Exhaustive methylation of GP–I–a gave 3,6-di-O-methyl derivative from the N-acetylglucosamine residues, and 2,3,4,6-tetra-O-methyl, 3,4,6-tri-O-methyI and 2,4-di-O-methyl derivatives from the mannose residues in an approximate ratio of 3: 1:2.

After one step of the Smith degradation of GP–I–a, a residual glycopeptide (F–1) consisted of one mole each of asparagine and glycine and two moles each of mannose and N-acetylglucosamine was obtained. Exhaustive methylation of F–1 gave 3,6-di-O-methyl derivative of N-acetylglucosamine, and 2,3,4,6-tetra-O-methyl and 2,3,4-tri-O-methyl derivatives of mannose in a ratio of 1.00: 0.91.

Partial acetolysis of 1→6 linkages in GP–I–a yielded mannose, 3-O-mannosylmannose and a smaller glycopeptide which was resistant to the acetolysis.

From these and other evidences, the following structure was determined for GP–I–a.     

Further Characterization of Carbohydrate-Containing Fractions from Trypanosoma mega1

Epimastigotes of Trypanosoma mega were submitted to phenol extraction after lipid extraction, providing an extract whose carbohydrate portion (30%) contained fucose, ribose, xylose, mannose, galactose, and glucose. The purified fraction recovered in the void volume of Bio Gel P-150 gave on SDS-PAGE a band of M_r～ 55,000 positive for protein and carbohydrate and a diffuse band strongly positive for carbohydrate and lipids (M_r～ 22,000). The structural analysis of the carbohydrate moiety of this fraction by GLC-MS indicated the presence of nonreducing end groups of fucopyranose, mannopyranose, and galactopyranose, 3-O- and 4-O-substituted and 2,3- and 2,4-di-O-substituted galactopyranosyl units. Extraction of this fraction with chloroform/methanol/water provided a soluble fraction that on SDS-PAGE gave rise to a carbohydrate and lipid-positive band (M_r～ 22,000). This fraction contained fucose, mannose, and galactose (1:1:1). As main branch points, 2,3-di-O-substituted galactopyranosyl units were present according to methylation data. Similar proportions of fucopyranosyl, mannopyranosyl, galactopyranosyl end units were present. The presence of lipids in this fraction was confirmed by methanolysis following isolation and characterization of the corresponding fatty acid methyl esters. Palmitic acid (16:0) and an 18:1 fatty acid were the predominant fatty acids.     

Methylation analysis of carrageenans from the seaweed Iridaea undulosa

Two carrageenans from Iridaea undulosa, isolated by precipitation of the crude polysaccharide at O.70–1.05 M and 1.55–1.65 M KCl concentrations, were studied by methylation analysis. Acid hydrolysis of the methylated derivative of the less soluble carrageenan (molar ratio galactose: 3,6-anhydrogalactose: sulphate 1.00: 0.50: 1.20) yielded major amounts of 2,6-di-O-methylgalactose (51.3 mol %), 4,6-di-O-methylgalactose (25.6%) and 4-O-methylgalactose (51.3mol%), 4,6-di-O-methylgalactose (25.6%) and 4-O-methylgalactose (13.4%). Minor quantities of 3-O-methylgalactose (4.6%) and 6-O-methylgalactose (3.2%) were found together with traces of 2,3,6- and/or 2,4,6-tri-O-methylgalactose, 2-O-methylgalactose and galactose. Oxidative acid hydrolysis produced 3,6-anhydro-2-O-methylgalactonic acid and 3,6-anhydrogalactonic acid in a molar ratio 3.5-4.0:1.0. The methylated derivative of the more soluble carrageenan (molar ratio galactose:3,6-anhydrogalactose:sulphate 1.00:0.04:1.43) gave on acid hydrolysis, 2,3,4,6-tetra-O-methylgalactose (4.6%), 2,3,6-tri-O-methylgalactose (4.2%), 2,4,6-tri-O-methylgalactose (10.7%), 4,6-di-O-methylgalactose (24.1%), 3,6-di-0-methylgalactose (8.0%), 2,3-di-O- methylgalactose (3.4%), 2,4-di-O-methylgalactose (4.6%), 2,6-di-O-methylgalactose (4.2%), 3-O-methylgalactose (19.5%),4-O-methylgalactose (9.6%),6-O-methylgalactose(3.1%),galactose (3.4%)and traces of 2-O-methylgalactose.     

The structure of bael (Aegle marmelos) gum

Purified, bael-gum polysaccharide containsd-galactose (71%),l-arabinose (12.5%),l-rhamnose (6.5%), andd-galacturonic acid (7%). Hydrolysis of one mole of the fully methylated polysaccharide gave: (a) from the neutral part, 2,3,4-tri-O-methyl-l-rhamnose (2 moles), 2,3,5-tri-O-methyl-l-arabinose (4 moles), 2,3,4,6-tetra-O-methyl-d-galactose (8 moles), 3,4-di-O-methyl-l-rhamnose (2 moles), 2,5-di-O-methyl-l-arabinose (1 mole), 2,4,6-tri-O-methyl-d-galactose (10 moles), 2,3-di-O-methyl-l-arabinose (1 mole), 2,4-di-O-methyl-d-galactose (14 moles), and 2-O-methyl-d-galactose (2 moles); and (b) from the acidic part, 2,3,4-tri-O-methyl-d-galacturonic acid (1 mole), 2,4,6-tri-O-methyl-3-O-(2,3,4-tri-O-methyl-d-galactopyranosyluronic acid)-d-galactose (2.6 moles), and 2,4,6-tri-O-methyl-3-O-[2,4,6-tri-O-methyl-3-O-(2,3,4-tri-O-methyl-d-galactopyranosyluronic acid)-d-galactopyranosyl]-d-galactose (1 mole). Mild hydrolysis of the whole gum yielded oligosaccharides from which 3-O-β-d-galactopyranosyl-l-arabinose, 5-O-β-d-galactopyranosyl-l-arabinose, 3-O-β-d-galactopyranosyl-d-galactose, and 6-O-β-d-galactopyranosyl-d-galactose could be isolated and characterized. The results of methylation, periodate oxidation, Smith degradation, Barry degradation, and graded hydrolysis studies were employed for the elucidation of the structure of the whole gum.     

Les polysaccharides des graines de quelques liliacees et iridacees

The alkali-soluble polysaccharides have been surveyed in the seeds of 7 species of the Liliaceae and 2 species of the Iridaceae. All appear to contain galactoglucomannans and/or glucomannans. The structure of the water-soluble galactoglucomannan from the endosperm of Asparagus officinalis has been studied in detail. It contains residues of glucose, mannose and galactose in the ratio 43:49:7. Hydrolysis of the fully methylated polysaccharide released 2,3,4,6-tetra-O-methyl-d-hexoses (mannose and glucose), 2,3,4,6-tetra-O-methyl-d-galactose, 2,3,6-tri-O-methyl-d-mannose, 2,3,6-tri-O-methyl-d-glucose, 2,3-di-O-methyl-d-mannose and 2,3-di-O-methyl-d-glucose in the molar proportions of 1:4.5:50:41:2:1·5. The following oligosaccharides were identified on partial hydrolysis of the galactoglucomannan: mannobiose, mannotriose, mannotetraose, cellobiose, glucopyranosylmannose, mannopyranosylglucose and a trisaccharide composed of two mannosyl residues and one glucosyl residue. The galactoglucomannan consists of a linear chain of β(1 → 4)-Iinked d-mannosyl and d-glucosyl residues, to which are attached single-unit galactosyl side chains. The galactose residues are linked 1 → 6, probably α. The terminal, non-reducing residues of the main chain may be either glucosyl or mannosyl units but the former predominate.     

Hemicellulosic polymers from the leaves of coffea arabica

Polysaccharide fractions from leaves of Coffea arabica var. Mundo Novo were obtained by extraction with 24% potassium hydroxide solution and were found to contain rhamnose, arabinose, xylose, mannose, galactose, glucose, glucuronic acid and 4-O-methylglucuronic acid in different proportions. 2-Acetamido-2-deoxygalactose was detected in all fractions. The structures of the carbohydrate portions were analysed by methylation and Smith degradation. A high amount of 2,3,5-tri-O-methylarabinose and 2,3,4-tri-O-methylxylose units, which are related through end groups, suggested a large degree of branching in the polysaccharide fractions. Glucose was present mainly as (1 → 4)-linked residues, as indicated by the presence of 2,3,6-tri-O-methylglucitol in the hydrolysates of the methylated fractions. A greater proportion of monomethylxylitol in acidic fraction B-IV indicated that it was more branched than the others. The glucose and galactose residues are 4,6- and 3,4-di-O-substituted, respectively. Three successive Smith degradations gave mainly glycerol with some erythritol and threitol. In the linkage of carbohydrate—protein, the presence of O-glycosyl linkages between arabinose and hydroxyproline was indicated. A phenolic compound was detected in all polysaccharide fractions from leaves of the coffee tree and is probably derived from chlorogenic acid.     

Structure of Cell Wall Polysaccharide Isolated from Cotyledon of Tora-bean (Phaseolus vulgaris)

The cell wall polysaccharide of cotyledon of Tora-bean (Phaseolus vulgaris), which surrounds starch granules, was isolated from saline-extraction residues of homogenized cotyledon, as alkali-insoluble fibrous substance. Alkali-insoluble residue, which had been treated with α-amylase (Termamyl), had a cellulose-like matrix under the electron microscope. It was composed of l-arabinose, d-xylose, d-galactose and d-glucose (molar ratio, 1.0: 0.2: 0.1: 1.2) together with a trace amount of l-fucose. Methylation followed by hydrolysis of the polysaccharide yielded 2, 3, 5-tri-O-methyl-l-arabinose (3.3 mol), 2, 3, 4-tri-O-methyl-d-xylose (1.0 mol), 2, 3-di-O-methyl-l-arabinose (3.7 mol), 3, 4-di-O-methyl-d-xylose (1.0 mol), 2-O-methyl-l-arabinose and 2, 3, 6-tri-O-methyl-d-glucose (12.7 mol), 2, 6-di-O-methyl-d-glucose (1.2 mol) and 2, 3-di-O-methyl-d-glucose (1.0 mol).

Methylation analysis, Smith degradation and enzymatic fragmentation with cellulase and α-l-arabinofuranosidase showed that the l-arabinose-rich alkali-insoluble polysaccharide possesses a unique structural feature, consisting of β-(1 → 4)-linked glucan backbone, which was attached with side chains of d-xylose residue and β-d-galactoxylose residue at O-6 positions and α-(1 → 5)-linked l-arabinosyl side cains (DP=8) at O-3 positions of β-(1 → 4)-linked d-glucose residues, respectively.     

Oxidation of 2,3,4,6-tetra-O-methyl-d-glucose with alkaline hydrogen peroxide

Treatment of 2,3,4,6-tetra-O-methyl-d-glucose with 10 molar equivalents ofn 30% aqueous hydrogen peroxide and 2 molar equivalents of potassium hydroxide afforded, after chromatographic separation, 2,3,4,6-tetra-O-methyl-d-gluconolactone. 1-O-formyl-2,3,5-tri-O-methyl-d-arabinose methyl hemiacetal (7), 2,3,5-tri-O-methyl-d-arabinonolactone, methyl 2,3,5-tri-O-methyl-d-arabinoside, O-(2,4-di-O-methyl-d-erythrose)-(1'→3)-2,4-di-O-methyl-d-erythronic acid, and O-(2,4-di-O-methyl-d-erythrose)-(1′→2)-3-O-methyl-d-glyceraldehyde. The proportions of the products depended on the reaction conditions, especially the time, temperature, and the presence or absence of magnesium hydroxide. Formation of the products is explained by a series of reactions beginning with the addition of hydrogen peroxide to the carbonyl form of the methylated sugar. The adduct, with the help of superoxide radical and a molecule of hydrogen peroxide, breaks up in two ways, giving 2,3,4,6-tetra-O-methyl-d-gluconic acid and 7. The formic ester, on hydrolysis, gives 2,3,5-tri-O-methyl-d-arabinose, which undergoes a similar series of reactions, affording 2,3,5-tri-O-methyl-d-arabinonic acid, and presumably, 1-O-formyl-2,4-di-O-methyl-d-erythrose methyl hemiacetal. Apparently, the latter compound, on hydrolysis, forms a dimer, which, with alkaline hydrogen peroxide, undergoes a similar series of reactions, ultimately affording O-(2,4-di-O-methyl-d-erythrose)-(1→3)-2,4-di-O-methyl-d-erythronic acid and O-(2,4-di-O-methyl-d-erythrose)-(1→2)-3-o-methyl-d-glyceraldehyde. With a larger amount of alkali, under more-severe conditions, oxidation of 2,3,4,6-tetra-O-methyl-d-glucose proceeds further, with production of up to 3 moles of formic acid per mole of methylated sugar.     

Heterogeneity of horse transferrin: the role of carbohydrate moiety

Homozygous horse transferrin (Tf O) is highly heterogeneous. In starch gel electrophoresis it gives at least 9 zones. Two main components (2a and 4b) were purified by rivanol and ammonium sulphate precipitation, DEAE-Sephadex chromatography and SP-Sephadex chromatography. Molecular weights of 75 200 and 80 500 for components 2a and 4b, respectively, were determined by sedimentation equilibrium ultracentrifugation. Amino acid compositions of the two components were similar, and there were no differences in the N-terminus (glutamic acid followed by glutamine) and the C-terminus (valine). Differences were found in carbohydrate composition between components 2a and 4b. Component 2a contained 10 moles of sugar components per mole of protein (4 hexoses, 4 hexosamines and 2 sialic acids), while component 4b contained twice the number of both total carbohydrates and individual sugar components. Carbohydrates were identified as mannose and galactose (ratio mannose: galactose approximately equal to 1.5:1), N-acetylglucosamine and N-acetylneuraminic acid. At present it is not clear whether the difference between the two components resides solely in the difference of carbohydrate contents. It is proposed that component 2a has one diantennary glycan, while component 4b has two.     

Synthesis of a model of an inner chain of cell-wall proteoheteroglycan isolated from Piricularia oryzae: Branched d-mannopentaosides

Efficient syntheses are described of the branched d-mannopentaosides methyl 2,6-di-O-(2-O-α-d-mannopyranosyl-α-d-mannopyranosyl)α-d-mannopyranoside and methyl 2,4-di-O-(2-O-α-d-mannopyranosyl-α-d-mannopyranosyl)-α-d-mannopyranoside, starting from the glycosyl acceptors methyl 3,4-di-O-benzyl-α-d-mannopyranoside and methyl 3,6-di-O-benzyl-α-d-mannopyranoside, and employing the protected d-mannotriosides methyl 3,4-di-O-benzyl-2,6-di-O-(3,4,6-tri-O-benzyl-α-d-mannopyranosyl)-α-d-mannopyranoside, and methyl 3,6-di-O-benzyl-2,4-di-O-(3,4,6-tri-O-benzyl-α-d-mannopyranosyl)-α-d-mannopyranoside as key intermediates.     

Carbohydrate composition of variant-specific surface antigen glycoproteins from Trypanosoma brucei

The carbohydrate of variant-specific surface antigen glycoproteins from bloodstream forms of 13 cloned variants of Trypanosoma brucei was analyzed by gas-liquid chromatography. The glycoproteins contained from 6 to 17% carbohydrate by weight, and all contained the same 4 sugars: mannose, galactose, glucose, and glucosamine (probably as N-acetylglucosamine). The glycoprotein from variant 048, strain 427 contained (+20%) 11 mannose, 4 galactose, 4 glucose, and 5 glucosamine residues/mole of glycoprotein (molecular weight 65,000). Glucose was an intergral component of the glycoproteins, not dissociable by sodium dodecyl sulphate, 8 M urea, or 1 M acetic acid. Some of the glucose was dissociated by trichloroacetic acid. Most of the glycoproteins formed precipitin with concanavalin A in Ouchterlony double diffusion, but none formed such bands with wheat germ agglutinin or Ricinus communis lectin (molecular weight 120, 000).     

Characterization of sheep hemopexin glycovariants

The hemopexin phenotype HpxB1 isolated from sheep serum, yields three major bands when subjected to starch gel and/or polyacrylamide gel electrophoresis which are here designated as subcomponents HpxB1-I, HpxB1-II and HpxB1-III. Electrospray mass spectrometric analysis of samples of the isolated subcomponents prepared by ion exchange chromatography showed that each was composed of three glycoproteins and that the major difference between the subcomponents was due to their constituent glycoproteins possessing different numbers of sialic acid residues. Combined analysis of the ESI-MS data and of the overall carbohydrate compositional data obtained by colorimetric procedures, leads to the composition of the glycan of each glycoprotein, and a combined methylation and 400 MHz H-NMR analysis of the alkaline cleaved glycans identified them as being of only the biantennaryN-acetyllactosamine type. Taking into account the molecular mass, the carbohydrate content and structure it may be concluded that each of the constituent glycoproteins contain fiveN-glycosidically linked glycans.Abbreviations HpxB1 hemopexin phenotype B1 - Man mannose - Gal galactose - GlcNAc N-acetylglucosamine - NeuAc N-acetylneuraminic acid - GlcNAc-ol N-acetylglucosaminitol     

Structure of Dextran Synthesized by Dextrin Dextranase from Acetobacter capsulatus ATCC 11894

The structure of dextran synthesized from maltotetraose by dextrin dextranase (EC 2.4.1.2) from Acetobacter capsulatus ATCC 11894 was analyzed. When the Acetobacter dextran (AD) was acetolyzed, glucose and maltose were produced. AD was allowed to react with α-amylases. AD was digested by bacterial saccharifying α-amylase and bacterial liquefying α-amylase, and glucose, maltose, and maltotriose were produced. The structure of the fraction obtained from dextranase-digested AD by activated charcoal chromatography, which did not contain glucose, isomaltose, and isomaltotriose, was investigated by methylation analysis, and the ratio of 2,3,4,6-tetra-O-methyl-: 2,3,4-tri-O-methyl-: 2,3,6-tri-O-methyl-: 2,3-di-O-methyl-alditol acetate was estimated as 22.9:46.8:15.5:14.8. This result indicated the existence of α-1,4 branches and that of α-1,4 linkages in α-1,6 glucosyl linear chains. Native AD was calculated to be constructed with 6.23 branching points and 6.53 α-1,4 linked glucosyl residues per 100 glucosyl units. Though AD was digested slightly by rat intestinal acetone powder, high molecular weight polymers remained. Therefore AD could be used as a dietary fiber.     

Compositional features of carbohydrate compound from rhizoma ligustici wallichii and ethanol extract of danshen and its bioactivity

Water extraction was applied to prepare carbohydrate compound of rhizoma ligustici wallichii. Four main fractions, fraction-I, fraction-II, fraction-III, and fraction-IV, were obtained by membranes of 1.0 × 10⁻⁴ mm pore size and normal molecular-weight cut-off of 50 kDa. The resulting four preparations were further analysed by capillary gas chromatography method. Thin layer chromatography (TLC) analysis showed that carbohydrate compound of rhizoma ligustici wallichii was composed of five types of monosaccharides, namely glucose, rhamnose, mannose, galactose and arabinose. Gas chromatography (GC) analysis showed that fraction I of rhizoma ligustici wallichii was composed of four types of monosaccharides, namely glucose, mannose, galactose and arabinose at a molar ratio of 521:1:4.6:3.3. Furthermore, the protective effect of the Rhizoma ligustici wallichii polysaccharides and ethanol extract of danshen against ischemia-reperfusion (IR) induced renal injury were evaluated. The findings imply that carbohydrate compound of the Rhizoma ligustici wallichii and ethanol extract of danshen play a causal role in IR-induced renal injury probably by the radical scavenging and antioxidant activities. Moreover, ethanol extract of danshen displayed stronger renoprotective effect than that of carbohydrate compound of the Rhizoma ligustici wallichii.     

Heterogeneity of horse transferrin: the role of carbohydrate moiety

Homozygous horse transferrin (Tf O) is highly heterogeneous. In starch gel electro-phoresis it gives at least 9 zones. Two main components (2a and 4b) were purified by rivanol and ammonium sulphate precipitation, DEAE-Sephadex chromatogra-phy and SP-Sephadex chromatography. Molecular weights of 75 200 and 80 500 for components 2a and 4b, respectively, were determined by sedimentation equilibrium ultracentrifugation. Amino acid compositions of the two components were similar, and there were no differences in the N -terminus (glutamic acid followed by glu-tamine) and the C -terminus (valine). Differences were found in carbohydrate composition between components 2a and 4b. Component 2a contained 10 moles of sugar components per mole of protein (4 hexoses, 4 hexosamines and 2 sialic acids), while component 4b contained twice the number of both total carbohydrates and individual sugar components. Carbohydrates were identified as mannose and galac-tose (ratio mannose:galactose = 1.5:l), N -acetylglucosamine and N -acetylneu-raminic acid. At present it is not clear whether the difference between the two components resides solely in the difference of carbohydrate contents. It is proposed that component 2a has one diantennary glycan, while component 4b has two.     

Selective benzylation of some D-galactopyranosides. Unusual relative reactivity of the hydroxyl group at C-4

Partial benzylation of methyl 2,3-di-O-benzyl-α-D-galactopyranoside gave methyl 2,3,6-tri-O-benzyl-α-D-galactopyranoside as the major product, whereas the isomeric 2,6-di-O-benzyl ether gave a mixture of products in which the ratio of methyl 2,4,6- to methyl 2,3,6-tri-O-benzyl-α-D-galactopyranoside was ≈4:1. The proportion of unreacted starting-material was low in both cases, whereas after a similar reaction of methyl 2,6-di-O-benzyl-β-D-galactopyranoside more than 50% of the dibenzyl ether was recovered unchanged. In this case also, considerably higher reactivity was exhibited by the hydroxyl group at C-4 than that at C-3. Acid hydrolysis of the methyl glycosides of the tribenzyl ethers afforded crystalline 2,4,6-tri-O-benzyl-α-D-galactose and syrupy 2,3,6-tri-O-benzyl-D-galactose. Structures of intermediates were established by acetylation, examination of their n.m.r. spectra, and conversion into the known 3-O and 4-O-methyl-D-galactose.     

Synthesis of 3,6-di-O-Methylglucosyl Disaccharides with Methyl 3-(p-Hydroxyphenyl)propionate as a Linker Arm and Their Use in the Serodiagnosis of Leprosy

The disaccharide, 2,3-di-O-methyl-4-O-(3,6-di-O-methyl-β-d-glucopyranosyl)-l-rhamno-pyranose, the distal segment of phenolic glycolipid I, that is a specific antigen from Mycobacterium leprae, and some related disaccharides were synthesised as the glycosides of methyl 3-(p-hydroxyphenyl)propionate. The methyl 3-(p-hydroxyphenyl)propionate was coupled with 2,3,4-tri-O-acetyl-l-rhamnosyl bromide, deacetylated, acetonated, coupled with 2,4,6-tri-O-acetyl-3-O-methyl-d-glucosyl bromide, and converted into a variety of p-(2-methoxycarbonylethyl)phenyl 4-O-(3,6-di-O-methyl-d-glucopyranosyl)-containing disaccharides that are amenable to ready conjugation with protein carriers, thereby providing neo-glycoconjugates for the specific serodiagnosis of leprosy.     

Structural investigations on two hemicellulosic polysaccharides from groundnut (Arachis hypogea) seed endosperm

A highly branched xylan and a linear, β-d-(1→4)-linked glucomannan are the two hemicellulosic components isolated from the endosperms of groundnut (Arachis hypogea). Electrophoretic, sedimentation, and sugar analysis indicate the polysaccharides to be fairly homogeneous. The O-methyl derivatives of the polysaccharides were analysed, after reduction and O-acetylation, by gas-liquid chromatography and g.l.c.-mass spectrometry. 2,3,4-Tri-O-methyl-d-xylose (3.6 mol), 2,3-di-O-methyl-d-xylose (21.0 mol), 3-O-methyl-d-xylose (2.8 mol), and d-xylose (4.2 mol) were detected in the xylan, whereas 2,3,4,6-tetra-O-methyl-d-glucose and/or mannose (1.6 mol), 2,3,6-tri-O-methyl-d-mannose (5.6 mol), and 2,3,6-tri O-methyl-d-glucose (21.2 mol) were found in the glucomannan. Periodate and Smith-degradation studies substantiate the results of methylation analysis on the xylan. A glucose: mannose ratio of 3:1 for the glucomannan, however, suggests that this fraction may be an aggregate of true glucomannan and glucan or degraded cellulose.     

Determination of structural elements of the L2/HNK-1 carbohydrate epitope required for its function

The L2/HNK-1 carbohydrate epitope has been shown to carry an unusual 3-sulfoglucuronic acid linkedO-glycosidically through a neolactosyl-type back bone to a ceramide residue. Using monoclonal antibodies, the same or a closely related epitope has also been detectedN-glycosidically linked to glycoproteins, amongst them several neural cell adhesion molecules. We used synthetic glycolipids carrying sulfated or non-sulfated glucuronic acid attached to ceramide through glycans of different length to show that not only the sulfated glucuronic acid but also the neolactosyl-type backbone is essential for the recognition of the L2/HNK-1 carbohydrate by a monoclonal antibody, its binding to laminin and its role in neural cell migration and outgrowth of processes from neurons and astrocytes.Abbreviations mab monoclonal antibody - TLC thin layer chromatography - HRP horseradish peroxidase - glcA glucuronic acid - gal galactose - glcNAc N-acetyl-glucosamine - man mannose