Smith degradation of gum exudates from some prosopis species

The polysaccharide of P. hymantophora has been shown to be composed of (1→4)-linked galactopyranosyl, (1→3)-linked galactopyranosyl, (1→3)-linked galactopyranosyl 2- and 4-sulphate and 2,6-disulphate residues. The (1→3)- and (1→4)-linked units are present in approximately equal amounts. The polysaccharide of P. hieroglyphica has been shown to possess (1→4)-linked galactopyranosyl, (1→3)-linked galactopyranosyl, and (1→3)-linked galactopyranosyl 2- and 4-sulphate residues. The (1→3)- and (1→4)-linked units are present in a 4:1 ratio. Both polysaccharides contain small proportions of non-reducing xylosyl end-groups.     

Structure of a galactomannan from Cassia alata seed

A water-soluble galactomannan, isolated from the seeds of Cassia alata Linn, has been investigated by using methylation analysis, periodate and CrO₃ oxidation, n.m.r. spectroscopy, and reaction with Bandeiraea simplicifolia lectin and an α-d-galactosidase. The polysaccharide is composed of heptasaccharide units joined by β-(1→4) linkages. The polysaccharide has a molecular weight of 26,400, corresponding to ∼23 units.     

Bis(2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-β-D-glucopyranosyl)amine obtained by a fusion reaction

A unique, alkali-soluble polysaccharide has been isolated from the cell walls of the basidiomycete Coprinus macrorhizus microsporus. The polysaccharide, which is primarily a glucan, contains a large proportion of α-(1→4)-linked d-glucose residues and a smaller amount of β-(1→3) and (1→6) linkages, as suggested by methylation, partial acid hydrolysis, periodate oxidation, and enzymic studies. Hydrolysis of the methylated polysaccharide gave equimolar amounts of 2,4-di- and 2,3-di-O-methyl-d-glucose; no 2,6-di-O-methyl-d-glucose was identified, indicating the absence of branch points joined through O-1, O-3, and O-4. The isolation and identification of 2-O-α- glucopyranosylerythritol from the periodate-oxidized polysaccharide suggests that segments of the a-(1→4)-linked d-glucose residues are joined by single (1→3)-linkages. An extracellular enzyme-preparation from Sporotrichum dimorphosporum (QM 806) containing both β-(1→3)- and α-(1→4)-d-glucanohydrolase activity released 76% of the reducing groups from the polysaccharide. The polysaccharide also contains minor proportions of xylose, mannose, 2-amino-2-deoxyglucose, and amino acids.     

Some structural features of a new sulphated heteropolysaccharide from Padina pavonia

An acid-extractable, water-soluble, polysaccharide sulphate, isolated from Padina pavonia, comprised variable proportions of glucuronic acid, galactose, glucose, mannose, xylose, and fucose in addition to a protein moiety. Partial acid hydrolysis and autohydrolysis of the free acid polysaccharide yielded several oligosaccharides. Evidence from periodate oxidation studies indicated that the inner polysaccharide portion is composed of (1 → 4)-linked β-D-glucuronic acid, (1 → 4)-linked β-D-mannose and (1 → 4)-linked β-D-glucose residues. The heteropolymeric partially sulphated exterior portion is attached to the inner part and comprises various ratios of (1 → 4)-linked β-D-galactose, β-D-galactose-3-sulphate residues, (1 → 4)-linked β-D-glucose residues, (1 → 2)-linked α-L-fucose 4-sulphate residues and (1 → 3)-linked β-D-xylose residues.     

Fine structure of (1→3),(1→4)-β-d-glucan from Zea shoot cell-walls

The insoluble material that remains after extraction of Zea shoots with cold buffer was treated successively with 3m LiCl and hot water. The polysaccharides solubilized by these treatments were mostly (1→3),(1→4)-β-d-glucans. The β-d-glucan from the hot-water-soluble fraction was hydrolyzed by Bacillus subtilis (1→3),(1→4)-β-d-glucan 4-glucanohydrolase. The oligosaccharides were characterized by methylation analysis of the enzymic fragments and by methylation analysis of secondary fragments generated by treatment of the isolated oligosaccharides with Streptomyces QM B814 cellulase. The results demonstrate that the native polysaccharide consists mainly of cellotriosyl and cellotetraosyl residues joined by single (1→3) linkages. Evidence is presented to show that certain other glucosyl sequences are also present in the native polysaccharide including (a) two, three, or four contiguous (1→3)-linkages; (b) blocks of more than four (1→4)-linked glucose residues; (c) regions having alternating (1→3)- and (1→4)-linkages.     

The galactan sulphate of the red alga Polysiphonia lanosa.

The structure of the galactan sulphate of P. lanosa has been established by a combination of methylation, treatment with alkali, and partial methanolysis of the alkali-treated polysaccharide to give derivatives of agarobiose. The polysaccharide belongs to the agar class, in which 3-linked derivatives of beta-D-galactose alternate with 4-linked derivatives of alpha-L-galactose in a repeating sequence. In addition to D-galactose itself, the 3-linked units include 6-O-methyl-D-galactose, D-galactose 6-sulphate, and a hitherto unreported unit, 6-O-methyl-D-galactose 4-sulphate. The 4-linked units include L-galactose 6-sulphate, 2-O-methyl-L-galactose 6-sulphate, and 3,6-anhydro-L-galactose.     

Chemical structure of an acidic polysaccharide produced by serratia piscatorum

The acidic polysaccharide of Serratia piscatorum consists of L-rhamnopyranosyl, D-galactopyranosyl, and D-galactopyranosyluronic acid residues in the molar ratio of 2:1:1. Some of the D-galactopyranosyluronic acid residues are acetylated at O-2 or O-3, or both. Smith degradation and methylation analysis indicated that the L-rhamnopyranosyl, D-galactopyranosyl, and D-galactopyranosyluronic acid residues are substituted with glycosidic linkages at O-3, O-3, and O-4, respectively. Partial acid hydrolysis of the native polysaccharide gave four acidic oligosaccharides, each of which was isolated and characterized, suggesting the following tetrasaccharide repeating unit: →3)-L-Rhap-(1→4)-D-GalAp-(1→3)-L-Rhap-(1→3)-D-Galp-(1→.     

Water- and alkali-soluble glucans from oak lichen

A water-soluble glucan, [α]²_D +217° (water), and an alkali-soluble glucan,

+152° (sodium hydroxide), have been isolated from the oak lichen Evernia prunastri (L.) Ach. On the basis of methylation analysis, periodate oxidation, and partial acid hydrolysis, the water-soluble polysaccharide has been shown to be a neutral, slightly branched glucan with a main chain composed of (1→3)- and (1→4)- linked glucopyranose residues in the ratio 1?:1. Branching occurs most probably at position 2 of (1→4)-linked glucopyranose residues. On the basis of optical rotation and i.r. spectral data, and enzymic hydrolysis, the α-D configuration has been assigned to the glycosidic linkages. Likewise, the alkali-soluble polysaccharide was shown to be a neutral, branched glucan with a main chain composed of (1→3)- and (1→4)-linked α-D-glucopyranose residues in the ratio 6:1. Each of the (1→4)-linked units was a branch point involving position 6. The presence of some β-D linkages is not excluded since hydrolysis with β-D-glucosidase occurred to a small extent.     

Structural investigations of the extracellular polysaccharide elaborated by s19, a Xanthomonas-type bacterium

The extracellular, acidic heteropolysaccharide from Xanthomonas S19 consists of D-glucuronic acid, D-glucose, D-galactose, and D-mannose residues in the approximate molar ratios of 1.6:3:1:1, plus acetyl groups liked to C-2 and/or C-3 of a large proportion of the glucose residues. Methylation studies showed that the glucose is present as non-reducing end-group also as 1,2- and 1,4-linked units, the galactose residues are solely 1,3-linked, a major proportion of the mannose residues are 1,2,4-linked and the rest 1,2-linked. A high proportion of the glucuronic acid units are 1,4-linked. Periodate oxidation confirmed the presence of these linkages. The disaccharides D-Glc-(1→4)-D-Glc,D-Glc-(1→2)-D-Man, D-Glc-(1→3)-D-Gal, D-Gal-(1→2)-D-Glc, D-GlcA-(1→4)-D-GlcA, and β-D-GlcA-(1→4)-D-Man were isolated from a partial hydrolysate of the polysaccharide, and characterised. The similarities and differences between this polysaccharide and those from other Xanthomonas species are discussed.     

Structural studies of the capsular polysaccharide elaborated by Haemophilus influenzae type d

The structure of the capsular polysaccharide elaborated by Haemophilus influenzae type d has been investigated, methylation analysis and n.m.r. spectrometry being the principal methods used. It is concluded that the polysaccharide is composed of repeating units having the structure: →4)-β-d-GlcpNAc-(1→3)-β-d-ManpNAcA-(1→. In addition, single residues of l-alanine, l-serine, or l-threonine, in the proportions 2:2:1, are linked, through their amino groups, to C-6 of the 2-acetamido-2-deoxy-β-d-mannopyranosyluronic acid residues. The degree of substitution (75-85%) varies for different preparations.     

The preparation of a crystalline guanosine trialcohol and its sodium salt

A polysaccharide has been extracted from Cassia corymbosa seeds with cold, acidulated water, and purified to give a water-soluble product containing d-galactose and d-mannose in 4:7 molar ratio. Acid-catalyzed fragmentation, periodate oxidation, methylation, and enzymic hydrolysis showed that the seed gum has a branched structure consisting of a linear chain of β-d-(1→4)-linked mannopyranosyl units, some of which are substituted at O-6 by two α-d-(1→6) galactopyranosyl units mutually linked glycosidically. Methylation analysis of the galactomannan afforded 2,3,4-tri- and 2,3,4,6-tetra-O-methylgalactose, along with 2,3-di- and 2,3,6-tri-O-methylmannose, in the molar ratios of 2:2:2:5. Both the methylation and the periodate-oxidation studies showed ～36.4% of end groups. The significance of these results, together with the findings of partial hydrolysis with acid, are discussed, in relation to ascertaining the structure of the repeating unit of the polysaccharide.     

Constitution of sargassan,a sulphated heteropolysaccharide from sargassum linifolium

The behaviour towards periodate of the brown-algal polysaccharide sargassan before and after partial hydrolysis, alkali treatment, and methanolysis has been studied. Evidence is thereby provided that the sargassan backbone is composed of (1→4)-linked β-D-glucuronic acid and β-D-mannose residues. Heteropolymeric, partially sulphated branches are attached to the backbone, and these branches comprise various proportions of(l→4)-linked, β-D-galactose, β-D-galactose 6-sulphate, and β-D-galactose 3,6-disulphate residues, (1→2)-linked α-L-fucose 4-sulphate residues, and (1→3)-linked β-D-xylose residues.     

An Alkali-soluble Polysaccharide from the oak lichen Cetraria islandica (L.) Ach.

An alkali-soluble polysaccharide, [α]

+43° (M sodium hydroxide), containing d-glucose and d-glucuronic acid has been isolated from the oak lichen Cetraria islandica (L.) Ach. On the basis of methylation, periodate oxidation, and partial hydrolysis studies, the polysaccharide has been shown to contain (1→3)-linked glucopyranose and glucuronic acid residues and (1→4)- and/or (1→6)-linked gluco-pyranose residues as the main structural features of the basic chain. A preponderance of β linkages, indicated by the low optical rotation and the i.r. spectrum, was corro-borated by the formation of laminaribiose, cellobiose, and gentiobiose on partial hydrolysis.     

Structure of the water-insoluble α-d-glucan of streptococcus salivarius HHT

Water-insoluble, non-adherent α-d-glucans have been obtained from Streptococcus salivarius HHT under two sets of conditions: from a growing culture, or synthesized enzymically by using a glucosyltransferase. In the former case, the glucan ([α]_d + 197°) was shown by methylation analysis to have a slightly branched structure containing a relatively high proportion (80 %) of (1→3)-α-d-glucosidic linkages, together with small proportions of (1→6)- and (1→4)-α-d-glucosidic linkages. The enzymically synthesized glucan had a much less-branched structure, containing 88 % of (1→3)-α-d-glucosidic linkages. Both glucans, on Smith degradation (sequential periodate oxidation, borohydride reduction, and mild acid hydrolysis), gave linear, (1→3)-α-d-glucosidic polysaccharides (yields, 82-90%) that constitute the backbone chains. The presence of small proportions of glycerol, erythritol, 1-O-α-d-glucosyl-d-glycerol, and also 2-O-α-d-glucosyl-d-erythritol in the products of Smith degradation suggests that the short side-chains are attached to the backbone chain by (1→4)-, (1→6)-, and (1→3)-α-d-glucosidic linkages     

Structural investigations on the non-starchy polysaccharides of oat bran

Digestion of oat bran with hog pancreatic α-amylase to hydrolyze starch (～50%) results in solubilization of much β-d-glucan (9%) which is the main non-starchy polysaccharide. This soluble β-d-glucan has been shown by methylation analysis and specific enzymic hydrolysis to contain linear chains with (1→3) and (1→4) linkages in the proportions 1 : 2·6. Compositional and linkage analysis studies on the water-insoluble residue have shown the presence of further β-d-glucan (5%) and arabinoxylan (3%), but only traces of cellulose (<0·5%).     

Structural studies on an antitumor polysaccharide from Microellobosporia grisea

The structure of the antitumor polysaccharide from the actinomycete Microellobosporia grisea has been investigated. By methylation and periodate-oxidation studies, the polysaccharide was shown to consist of (nonreducing)d-mannosyl groups, (1→4)-linkedd-glucosyl residues, and 3,6-branched, (1→4)-linkedd-glucosyl residues in the approximate molar ratios of 2:1:1. Periodate oxidation of the polysaccharide, followed by borohydride reduction and mild hydrolysis with acid yielded glycerol, erythritol, 2-O-β-d-glucopyranosyl-d-erythritol, and 5-O-β-d-glucopyranosyl-2,4-bis(hydroxymethyl)-1,3-dioxane, which were isolated in the molar ratios of 2.0:0.14:0.74:0.35. Partial hydrolysis of the polysaccharide gave α-d-Man p-(1→6)-d-Glcp, β-d-Glcp-(1→4)-d-Glcp, α-d-Man p-(1→3)-d-Glcp, and β-d-Glcp-(1→4)-[α-d-Man p-(1→3)-]-d-Glcp. From these results, it is proposed that the polysaccharide is mainly composed of tetrasaccharide repeating-units having the following structure.     

Structural analysis of suisen glucomannan

The main component of the mucilage in the bulbs of Suisen (Narcissus tazetta L., var. chinensis Roem) has been shown to be a glucomannan composed of D-glucose and D-mannose in the ratio of 2:3 and having a relatively low degree of branching. Acetolysis of the polysaccharide led to the isolation of β-(1→4)-β-(1→3)-linked oligosaccharides composed of D-mannose and/or D-glucose residues. The average chain length (c.1.) of the polysaccharide was determined by methylation analysis to be about 22.     

Structure of a new galactomannan from the ascocarps of Cordyceps cicadae shing

A water-soluble galactomannan (C-3), [α]_D²⁰ +30°, isolated from the rod-like ascocarps of Cordyceps cicadae, was determined to be homogeneous, and the molecular weight was estimated by gel filtration to be 27,000. The polysaccharide is composed of d-mannose and d-galactose in the molar ratio of 4:3. The results of methylation analysis, Smith degradation, stepwise hydrolysis with acid, and ¹³C-n.m.r. spectroscopy indicated that the polysaccharide is of highly branched structure, and composed of α-d-(1→2)-linked and α-d-(1→6)-linked mannopyranosyl residues in the core; some of these residues are substituted at O-6 and O-2 with terminal β-d-galactofuranosyl and α-d-mannopyranosyl groups, and with short chains of β-d-(1→2)-linked d-galactofuranosyl units.     

Structural studies of water-soluble glycoproteins from Cannabis sativa L

Two carbohydrate-protein fractions, isolated from Cannabis sativa L. by extraction with water and chromatography on DEAE-cellulose, contained arabinose, galactose, glucose, mannose, galacturonic acid, 2-acetamido-2-deoxyglucose, and 2-acetamido-2-deoxygalactose. The structure of the carbohydrate moieties was investigated by methylation analysis and Smith degradation. A high percentage of end-groups indicates a large degree of branching, glucose and galactose being the main branch-points, linked at C-3 and C-6. The hexoses are also present as unbranched residues in the chain, largely as (1→3)- and (1→4)-linked units and as end-groups. Arabinofuranosyl units constitute the main part of the non-reducing end-groups, and are also present as part of the chain. The polysaccharide chains are probably linked to protein through the hydroxyl group of hydroxyproline.     

Conformational Studies of β-glucans

Steric and energy contour diagrams have been plotted for disaccharide-like and for helical structures of linear β-D -glucans having (1 → 2), (1 → 3) and (1 → 4) linkages. The allowed conformations constitute only about. 4% of the total conformations, indicating that the freedom of rotation of glucose residues is highly restricted in all the three polysaccharides. The additional restrictions of the monomer unit, as one passes from disaccharide to polysaccaride structures, are severe in the case of (1 → 2) and (1 → 3) linked polysaccharides but not in (1 → 4) linked polysaccharide. The difference in the nature of linkages also has shown to affect the energetically preferred conformations: (1 → 2) linkages lead only to left handed helical conformations; (1 → 3) linkages lead to both right and left handed wide and extended helical conformations, (1 → 4) linkages lead to both right and left handed extended helical conformations. The possible hydrogen bonds between adjacent residues are also dependent on the nature of linkage.