Application of anhydrous hydrogen fluoride for the structural analysis of polysaccharides

Significance of root hairs in developing stress-resilient plants for sustainable crop production

Root hairs represent a beneficial agronomic trait to potentially reduce fertilizer and irrigation inputs. Over the past decades, research in the plant model Arabidopsis thaliana has provided insights into root hair development, the underlying genetic framework and the integration of environmental cues within this framework. Recent years have seen a paradigm shift, where studies are now highlighting conservation and diversification of root hair developmental programs in other plant species and the agronomic relevance of root hairs in a wider ecological context. In this review, we specifically discuss the molecular evolution of the RSL (RHD Six-Like) pathway that controls root hair development and growth in land plants. We also discuss how root hairs contribute to plant performance as an active physiological rooting structure by performing resource acquisition, providing anchorage and constructing the rhizosphere with desirable physical, chemical and biological properties. Finally, we outline future research directions that can help achieve the potential of root hairs in developing sustainable agroecosystems.

Structure elucidation and gene cluster annotation of the O-antigen of Escherichia coli O39; application of anhydrous trifluoroacetic acid for selective cleavage of glycosidic linkages

O-Polysaccharide (O-antigen) accompanied by a minor mannan was isolated from the lipopolysaccharide of Escherichia coli O39 and studied by component analyses, methylation, Smith degradation, mass spectrometry, and 1D and 2D NMR spectroscopy. In addition, a new approach, solvolysis with anhydrous trifluoroacetic acid, was applied to cleave selectively the rhamnosidic linkage. The following structure of the O-polysaccharide was established: α--D-Galpl-->3-->3)-β-D-Quip4N(R3Hb)-(1-->2)-α-D-Manp-(l-->4)-α-L-Rhap-(1-->3)-α-D-GlcpNAc-(1--> where D-Qui4N(R3Hb) indicates 4,6-dideoxy-4-[(R)-3-hydroxybutanoylamino]-d-glucose. The O-antigen gene cluster of E. coli O39 has been sequenced. The gene functions were tentatively assigned by a comparison with sequences in the available databases and found to be in agreement with the O-polysaccharide structure.

Development and persistence of sandsheaths of Lyginia barbata (Restionaceae): relation to root structural development and longevity

BACKGROUND AND AIMS

Strongly coherent sandsheaths that envelop perennial roots of many monocotyledonous species of arid environments have been described for over a century. This study, for the first time, details the roles played by the structural development of the subtending roots in the formation and persistence of the sheaths.

METHODS

The structural development of root tissues associated with persistent sandsheaths was studied in Lyginia barbata, native to the Western Australian sand plains. Cryo-scanning electron microscopy CSEM, optical microscopy and specific staining methods were applied to fresh, field material. The role of root hairs was clarified by monitoring sheath development in roots separated from the sand profile by fine mesh.

KEY RESULTS AND CONCLUSIONS

The formation of the sheaths depends entirely on the numerous living root hairs which extend into the sand and track closely around individual grains enmeshing, by approx. 12 cm from the root tip, a volume of sand more than 14 times that of the subtending root. The longevity of the perennial sheaths depends on the subsequent development of the root hairs and of the epidermis and cortex. Before dying, the root hairs develop cellulosic walls approx. 3 µm thick, incrusted with ferulic acid and lignin, which persist for the life of the sheath. The dead hairs remain in place fused to a persistent platform of sclerified epidermis and outer cortex. The mature cortex comprises this platform, a wide, sclerified inner rim and a lysigenous central region - all dead tissue. We propose that the sandsheath/root hair/epidermis/cortex complex is a structural unit facilitating water and nutrient uptake while the tissues are alive, recycling scarce phosphorus during senescence, and forming, when dead, a persistent essential structure for maintenance of a functional stele in the perennial Lyginia roots.

Structure of the O-polysaccharide of Proteus mirabilis O38 containing 2-acetamidoethyl phosphate and N-linked d-aspartic acid

The O-antigen of Proteus mirabilis O38 was found to be unique among bacterial polysaccharides and to have the following structure: [carbohydrate structure in text] where D-Qui4N(Ac-D-Asp) is 4-(N-acetyl-D-aspart-4-ylamino)-4,6-dideoxy-D-glucose and AcEtnP is 2-acetamidoethyl phosphate. Neither of these entities have been hitherto found in natural polysaccharides. Structural studies were performed using 1D and 2D NMR spectroscopy, including experiments run in an H2O/D2O mixture to reveal correlations for NH protons. In addition, dephosphorylation, carboxyl reduction and selective cleavages were applied. Solvolysis of the polysaccharide with anhydrous HF gave an alpha-D-GlcNAc-(1-->3)-D-Qui4N(Ac-D-Asp) disaccharide. Solvolysis with trifluoromethanesulfonic (triflic) acid afforded D-GlcNAc6(AcEtnP), thus showing the suitability of this reagent for the preparation of phosphorylated sugar derivatives.

Isolation and characterisation of the homogalacturonan from type II cell walls of the commelinoid monocot wheat using HF-solvolysis

In contrast to the typical type I cell wall of the dicot plants, the type II cell wall of the commelinoid monocot plants is known to be relatively poor in pectins. Assuming a critical role for the remaining pectins in terms of cell wall architecture and/or as a reservoir of signalling molecules, we have compared different protocols for the isolation of the main pectin polymer, homogalacturonan, from wheat leaf cell walls. Pectin was detected in these cell walls immunochemically using the monoclonal antibodies JIM5 and JIM7, and biochemically by monosaccharide analysis. The Ca(++)-chelators CDTA and imidazole extracted a pectin rich fraction from isolated cell walls which was however contaminated with significant amounts of hemicelluloses. Pretreatment of the cell walls with anhydrous hydrogen fluoride at controlled low temperatures followed by HF/ether- and water-extraction prior to imidazole-extraction of pectins yielded a purer homogalacturonan fraction. The near absence of rhamnosyl residues proved that the isolated homogalacturonan fraction was free of rhamnogalacturonans. If HF-solvolysis was performed at -23 degrees C, the resulting homogalacturonan had a degree of methyl esterification identical to that of the pectins in the initial wheat cell wall. The antibodies JIM5 and JIM7 as well as PAM1 and LM5 proved that the isolated homogalacturonan had a low methyl ester content, was polymeric and free of galactan side chains. We can thus isolate native homogalacturonan from the type II wheat cell walls with the original in muro pattern of methyl esterification still intact, to further investigate e.g., its degradability by plant or microbial pectic enzymes.

Structure of the acidic O-specific polysaccharide from Proteus vulgaris O39 containing 5,7-diacetamido-3,5,7,9-tetradeoxy-L-glycero-L-manno-non-2-ulosonic acid

The O-specific polysaccharide of Proteus vulgaris O39 was found to contain a new acidic component of Proteus lipopolysaccharides, 5,7-diacetamido-3,5,7,9-tetradeoxy-L-glycero-L-manno-non-2-ulosonic acid (di-N-acetylpseudaminic acid, Pse5Ac7Ac). The following structure of the polysaccharide was determined by NMR spectroscopy, including 2D 1H,(1)H COSY, TOCSY, ROESY, and 1H,(13)C HMQC experiments, along with selective cleavage of the polysaccharide by solvolysis with anhydrous trifluoromethanesulfonic (triflic) acid: -->8)-beta-Psep5Ac7Ac-(2-->3)-alpha-L-FucpNAc-(1-->3)-alpha-D-GlcpNAc-(1--> The structure established is unique among the O-specific polysaccharides, which is in accordance with classification of the strain studied into a separate Proteus serogroup.

Structural studies of the O-specific polysaccharide of Vibrio cholerae O8 using solvolysis with triflic acid

The O-specific polysaccharide (OPS) of Vibrio cholerae 08 was isolated by mild acid degradation of the lipopolysaccharide and studied by two-dimensional NMR spectroscopy, including NOESY and heteronuclear multiple-bond correlation (HMBC) experiments. The OPS was found to have a tetrasaccharide repeating unit with the following structure: --> 4)-beta-D-Glcp NAc3NAcylAN-(1 --> 4)-beta-D-Manp NAc3NAcAN-(1 --> 4)-alpha-L-Gulp NAc3NAcA-(1 --> 3) -beta-D-QuipNAc4NAc-(1 --> where QuiNAc4NAc is 2,4-diacetamido-2,4,6-trideoxyglucose, GlcNAc3NAcylAN is 2-acetamido-3-(N-formyl-L-alanyl)amino-2,3-dideoxyglucuronamide, ManNAc3NAcAN is 2,3-diacetamido-2,3-dideoxymannuronamide, and GulNAc3NAcA is 2,3-diacetamido-2,3-dideoxyguluronic acid. The OPS was stable towards acid hydrolysis and solvolysis with anhydrous hydrogen fluoride, but could be cleaved selectively with trifluoromethanesulfonic (triflic) acid by the glycosidic linkages of beta-QuiNAc4NAc and alpha-GulNAc3NAcA. The structures of the oligosaccharides obtained that were elucidated by electrospray ionization (ESI) MS and NMR spectroscopy, confirmed the OPS structure.

Isolation using triflic acid solvolysis and identification of N(epsilon)-[(R)-1-carboxyethyl]-N(alpha)-(D-galacturonoyl)-L-lysine as a component of the O-specific polysaccharide of Proteus mirabilis O13

An amino acid was released from the O-specific polysaccharide of Proteus mirabilis O13 by acid hydrolysis and identified as N(epsilon)-[(R)-1-carboxyethyl]-L-lysine by comparison with the authentic sample. An amide of this amino acid with D-galacturonic acid was isolated from the polysaccharide by solvolysis with anhydrous trifluoromethanesulfonic (triflic) acid and characterised by 1H and 13C NMR spectroscopy. These and published data enabled determination of the full structure of the repeating unit of the polysaccharide.

Structure of an O-acetylated acidic O-specific polysaccharide of Proteus vulgaris O46

An acidic O-specific polysaccharide was obtained by mild acid degradation of the lipopolysaccharide of Proteus vulgaris O46 and studied by chemical methods (O-deacetylation, sugar and methylation analyses, partial solvolysis) and 1H and 13C NMR spectroscopy. Solvolysis of the O-deacetylated polysaccharide with trifluoromethanesulfonic acid resulted in a alpha-D-GlcpNAc-(1 --> 3)-D-GlcA disaccharide that demonstrated the usefulness of this reagent for selective cleavage of heteropolysaccharides. The following structure for the polysaccharide was established: --> 4)-alpha-D-Glcp6Ac(1 --> 3)-beta-D-GlcpA4Ac-(1 --> 3)-alpha-D-GlcpNAc-(1 --> 3)-beta-D-GlcpA4Ac-(1 --> where the degree of O-acetylation is approximately 65% at position 6 of Glc and 80-95% at position 4 of GlcA residues.

Determination of amino acids in diverse polymeric matrices using HPLC, with emphasis on agars and agaroses

Determination of amino acids in polymers with varying structure and charge was performed using vapor phase acid hydrolysis and subsequent precolumn derivatization with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC). Percent load of neutral, cationic and anionic peptide-modified synthetic polymers was accurately determined using this technique. Assay utility was shown for glycosaminoglycans and other sulfated polymers, neutral carbohydrate polymers such as agar, agarose, and cellulose, and polymers such as lipopolysaccharide and deoxyribonucleic acid. The carboxylated and sulfated molecules included chondroitin sulfate, hyaluronic acid, dermatan sulfate, and heparin, and the sulfated polymers included fucoidan, carrageenan, and dextran sulfate, as examples. Assayed cumulative amino acid concentrations (i.e. protein levels) are reported, although amino acid distribution data was also available from the analysis. Recovery was acceptable for the various compounds tested and did not correlate with structure. However, different sample sizes were necessary to achieve acceptable recovery, depending on the level of protein present in the matrix. While some matrices contained peaks in addition to the amino acids and amino sugars, they were not found to interfere using the standard gradient separation. Assayed amino acid profiles were compared for agaroses with differing electroendosmosis values and for agar samples from different parts of the globe. While the amounts of protein varied depending on source, the relative distribution of amino acids was very similar across the agar samples surveyed.

Structure determination of an exopolysaccharide from an alkaliphilic bacterium closely related to Bacillus spp

An exopolysaccharide obtained from an alkaliphilic bacterium closely related to Bacillus spp. was found to contain D-galactopyranuronic acid (GalpA), 2,4-diacetamido-2,4,6-trideoxy-D-glucopyranose (QuipNAc4NAc), 2-acetamido-2-deoxy D-mannopyranuronic acid (ManpNAcA) and one uncommon unit of D-galactopyranuronic acid with the carboxyl group amide-linked to glycine [GalpA(Gly)]. The polysaccharide was studied by one-dimensional and two-dimensional 1H-NMR and 13C-NMR spectroscopy both on native polysaccharide and on monosaccharides and oligosaccharides obtained from methanolysis and from anhydrous HF solvolysis. The following linear structure of the repeating unit was established: -->3)-alpha-D-GalpA(Gly)-(1-->4)-beta-D-ManpNAcA-(1-->4)-alp ha-D-Galp A-(1-->3)-alpha-D-QuipNAc4NAc-(1-->. A preliminary phylogenetic assignment for the bacterium is also reported.

Structure of stewartan, the capsular exopolysaccharide from the corn pathogen Erwinia stewartii

Stewartan, the acidic exopolysaccharide of Erwinia stewartii, was purified from agar grown cells. To facilitate its structural analysis, chemical and enzymatic depolymerizations were carried out using hydrofluoric acid and E. amylovora phage phi-Ea1h, respectively. Structural characterization of the resulting oligosaccharides was performed by a combination of mass spectrometric and one- and two-dimensional (1D/2D) NMR spectroscopic techniques. A branched repeating unit with seven monosaccharide residues, all in their pyranose forms, was found: [Table: see text]

Structure of amylovoran, the capsular exopolysaccharide from the fire blight pathogen Erwinia amylovora

The acidic exopolysaccharide (EPS) of Erwinia amylovora, amylovoran, was purified from culture supernatants of bacteria in minimal medium and cleaved chemically either by treatment with trifluoracetic acid or hydrofluoric acid, and enzymatically by digestion with depolymerase from E. amylovora phage phi-Ealh. Structural characterization of the resulting oligosaccharides was performed by a combination of mass spectrometric and NMR [one- and two-dimensional (1D and 2D)] spectroscopic techniques. A branched repeating unit with five monosaccharide residues and various substituents was determined: [sequence: see text] The terminal monosaccharide of the side branch, which bears a 4,6-bound pyruvate residue in the R-configuration, was found to be modified with 2-linked (26%), 3-linked (24%), 2-,3-linked (40%) O-acetyl groups, or these were absent (10%). An additional glucose residue is linked to approximately 10% of the core alpha-galactose of the repeating unit.

Structure of the Hafnia alvei strain PCM 1188 O-specific polysaccharide

The lipopolysaccharide was extracted from cells of Hafnia alvei PCM 1188 strain and, after mild acid hydrolysis, the O-specific polysaccharide isolated and characterized. On the basis of sugar and methylation analysis, FAB mass spectrometry and NMR spectroscopy of the polysaccharide and oligosaccharides obtained after Smith degradation, or solvolysis with anhydrous hydrogen fluoride, the repeating unit of the O-specific polysaccharide was shown to be the pentasaccharide: [formula: see text]

Structure of simusan, a new acidic exopolysaccharide from Arthrobacter sp

Simusan, a major exopolysaccharide produced by an ethanol-utilizing Arthrobacter sp. strain CE-17, contains D-glucose, D-mannose, D-galactose, L-rhamnose, D-glucuronic acid, and pyruvic acid in the ratios approximately 3:2:1:1:1:1 as well as O-acyl groups (presumably (presumably residues of acetic and palmitic acid). On the basis of chemical modifications of the polysaccharide, solvolysis with anhydrous hydrogen fluoride resulting in a penta- and an octa-saccharide fragment, Smith degradation, and 1H and 13C NMR analysis, the following structure of the repeating unit was established: [formula: see text] It is suggested that at least one of the glucose residues and the galactose residue are O-acetylated.

Structure of the Acetobacter methanolicus MB 129 capsular polysaccharide, and of oligosaccharides resulting from degradation by bacteriophage Acm7

The capsular polysaccharide of Acetobacter methanolicus MB 129 consists of D-Glc, D-Gal, L-Rha, and L-glyceric acid in the molar ratios 1:1:1:0.3. Periodate oxidation, methylation analysis, solvolysis with HF, and detailed 1H and 13C NMR analysis resulted in the structure of the repeating unit shown below. [formula: see text] Bacteriophage Acm7-associated end-alpha-L-rhamnopyranoside hydrolase depolymerizes the CPS even in the presence of the O-acyl group, to give the respective hexa-, nona-, and dodeca-saccharides.

Escherichia coli K48 capsular polysaccharide: a glycan containing a novel diacetamido sugar

The structure of the exocellular capsular polysaccharide expressed by Escherichia coli O8:K48:H9 has been investigated by hydrolysis and methylation analysis, and by NMR spectroscopic studies of the polysaccharide and of the oligosaccharides generated by solvolysis with anhydrous HF. The capsular polysaccharide was shown to have the repeating unit: [formula: see text] where beta-L-Sug p represents 2,3-diacetamido-2,3,6-trideoxy-beta-L- mannopyranose.

Synthesis of dispirodioxanyl pseudo-oligosaccharides by selective protonic activation of isomeric glycosylfructoses in anhydrous hydrogen fluoride

Dispirodioxanyl pseudotetrasaccharides 6-O-alpha-D-glucopyranosyl-alpha-D-fructofuranose 6-O-alpha-D-glucopyranosyl-beta-D-fructofuranose 1,2':2,1'-dianhydride, 5-O-alpha-D-glucopyranosyl-alpha-D-fructopyranose 5-O-alpha-D-glucopyranosyl-beta-D-fructopyranose 1,2':2,1'-dianhydride, 4-O-alpha-D-glucopyranosyl-alpha-D-fructofuranose 4-O-alpha-D-glucopyranosyl-beta-D-fructopyranose 1,2':2,1'-dianhydride, 4-O-beta-D-galactopyranosyl-alpha-D-fructofuranose 4-O-beta-D-galactopyranosyl-beta-D-fructopyranose 1,2':2,1'-dianhydride, and 3-O-alpha-D-glucopyranosyl-alpha-D-fructofuranose 3-O-alpha-D-glucopyranosyl-beta-D-fructofuranose 1,2':2,1'-dianhydride were respectively obtained, on a preparative scale, by dissolution of the isomeric glycosylfructoses palatinose, leucrose, maltulose, lactulose, and turanose in anhydrous hydrogen fluoride. The reaction, involving selective protonation at the free anomeric position of the fructose unit, was extended to the preparation of the pseudotrisaccharides 6-O-alpha-D-glucopyranosyl-alpha-D-fructofuranose beta-D-fructopyranose 1,2':2',1-dianhydride from palatinose and fructose, and to its 3-O-, 4-O-, and 4'-O-glucosyl analogues using turanose and maltulose as the disaccharide precursor. The cross-reactions of palatinose with maltulose and with leucrose resulted in the preparation of 6-O-alpha-D-glucopyranosyl-alpha-D-fructofuranose 4-O-alpha-D-glucopyranosyl-beta-D-fructopyranose 1,2':2,1'-dianhydride and 6-O-alpha-D-glucopyranosyl-alpha-D-fructofuranose 5-O-alpha-D-glucopyranosyl-beta-D-fructopyranose 1,2':2,1'-dianhydride, respectively.

Protonic reactivity of sucrose in anhydrous hydrogen fluoride

Sucrose reacts quantitatively, when dissolved at high concentration in anhydrous hydrogen fluoride, to afford a complex mixture of difructose dianhydrides and their glucosylated derivatives. Oligo- and small poly-saccharides up to dp 14 were detected by FABMS. Oligosaccharides up to dp 4, representing approximately 50% of the total mixture, have been isolated and characterized by mass spectrometry, 13C NMR spectroscopy, and comparison with reference oligosaccharides previously obtained by unambiguous synthesis. alpha-D-Fructofuranose beta-D-fructopyranose 1,2':2,1'-dianhydride is the main spirodioxanyl pseudodisaccharide entity found in the mixture, either free or glucosylated at C-6 and to a lesser extent at C-3, C-4, C-4', C-6, and C-5' C-6. Minor spirodioxanyl pseudodisaccharide components are di-beta-D-fructopyranose 1,2':2,1'-dianhydride, which has also been found glucosylated at C-5, alpha-D-fructopyranose beta-D-fructopyranose 1,2':2,1'-dianhydride, beta-D-fructofuranose beta-D-fructopyranose 1,2':2,3'-dianhydride, and the 6,6'-diglucosylated alpha-D-fructofuranose beta-D-fructofuranose 1,2':2,1'-dianhydride. A 13C NMR examination of the higher mass oligomeric fraction suggests that it may involve 6-O-isomaltooligoglycosyl alpha-D-fructofuranose beta-D-fructopyranose 1,2':2,1'-dianhydrides as the main structural components. The reaction of sucrose in anhydrous HF is believed to proceed through initial selective protonic activation of the tertiary anomeric carbon atom of the fructose moiety, resulting in the quantitative formation of difructose dianhydrides, which subsequently suffer electrophilic substitution by glucopyranosyl oxocarbenium ions generated in a second step by action of the HF.

Structural studies of the Vibrio cholerae O:5 O-antigen polysaccharide

The O-polysaccharide from Vibrio cholerae O:5 has been investigated, using NMR spectroscopy as the main method. Fast atom bombardment mass spectrometry (FABMS) studies of fragments obtained on treatment with anhydrous hydrogen fluoride or methanolic hydrogen chloride gave further structural information. Some structural features were also determined by comparison of nuclear Overhauser enhancement (NOE) contacts with calculated H-H distance in different oligosaccharide models. It is concluded that the O-polysaccharide has the following structure, in which D-Qui p NAc4NAc is 2,4-diacetamido-2,4,6-trideoxy-D-glucose, and D-Fuc p 3NX is 3-amino-3,6-dideoxy-D-galactose acylated with a (R,R)-3-hydroxy-3-methyl-5-oxoproline group. [formula: see text]

Structural studies of the Escherichia coli O127 O-antigen polysaccharide

The O-specific side-chain of the lipopolysaccharide from Escherichia coli O127a:H- (O127a:4932-53) has been investigated using 2D NMR spectroscopy, methylation analysis, and partial solvolysis with anhydrous hydrogen fluoride as the principal methods. It is concluded that the polysaccharide is composed of tetrasaccharide repeating-units having the following structure. -->2)-alpha-L-Fucp-(1-->2)-beta-D-Galp-(1-->3)-alpha-D-GalpNAc-(1- ->3)-alpha-D- GalpNAc-(1--> The polysaccharide contains approximately one mole of O-acetyl groups per repeating unit distributed over several positions.

Structure of the O-specific polysaccharide of Salmonella arizonae O45

The O-specific polysaccharide of Salmonella arizonae O45 (Arizona 11) is acidic and has a branched hexasaccharide repeating unit containing two residues of L-fucose, one residue each of D-galactose, D-ribose, D-glucuronic acid, and 2-acetamido-2-deoxy-D-glucose, and an O-acetyl group. It was studied with the help of 1H and 13C NMR spectroscopy, including 1D selective spin-decoupling and homonuclear Hartmann-Hahn spectroscopy, 2D homonuclear and 13C-1H heteronuclear shift-correlated (COSY) and NOE (ROESY) spectroscopy, as well as by methylation analysis, and selective cleavages with anhydrous HF (or dilute HCl) and lithium in ethylenediamine to yield two different tetrasaccharide fragments. As a result, the following structure of the polysaccharide was established: [formula: see text] Anomalous 13C chemical shifts were observed in the spectrum of the trisaccharide fragment alpha-L-Fucp-(1-->2)-beta-D-Gal p-(1-->3)-beta-D-Glc pNAc, structurally related to the Le(d) blood-group determinant, and rationalised by inter-residue proton-proton interactions.

Structure of the repeating unit of the O-specific polysaccharide of the lipopolysaccharide of Yersinia kristensenii strain 490 (O:12,25)

The O-specific polysaccharide isolated by mild acid degradation of the lipopolysaccharide of Y. kristensenii strain 490 (O:12,25) contained D-glucose, 2-acetamido-2-deoxy-D-glucose, 2-acetamido-2-deoxy-D-galactose, 2-acetamido-2,6-dideoxy-L-galactose, glycerol, and phosphate in the ratios 2:2:1:1:1:1. On the basis of 31P- and 13C-n.m.r. data, methylation analysis, dephosphorylation, solvolysis with anhydrous hydrogen fluoride, and Smith degradation, it was concluded that the repeating unit of the polysaccharide was a branched hexaosylglycerol phosphate with the following structure. [formula: see text]

Carbohydrate composition analysis of bacterial polysaccharides: optimized acid hydrolysis conditions for HPAEC-PAD analysis

The capsular polysaccharide from Haemophilus influenzae type b (polyribosyl ribitol-phosphate; PRP) and the capsular polysaccharides from Streptococcus pneumoniae types 6B, 14, 18C, and 23F (Pn6B, Pn14, Pn18C, and Pn23F) were subjected to acid hydrolysis using hydrofluoric (HF) and/or trifluoroacetic acid (TFA) and high-pH anion-exchange chromatography with pulsed amperometric detection in an effort to identify optimum hydrolysis conditions for composition analysis of their carbohydrate components. With the exception of PRP, composition analyses of polysaccharides containing a phosphate moiety in the repeating unit structure (Pn6B, Pn18C, and Pn23F) are significantly improved by subjecting the sample to HF hydrolysis (65 degrees C, 1 h) followed by TFA hydrolysis (98 degrees C, 16 h). This results in essentially quantitative hydrolysis of the phosphodiester bond to the carbohydrate components, which otherwise remained predominantly phosphorylated and poorly accounted for in the analysis. Optimum analysis of PRP was achieved following a 2-h hydrolysis with TFA at 80 degrees C, whereas Pn14 showed optimum results after a 16-h hydrolysis with TFA at 98 degrees C. These analyses also provide information about the relative susceptibility to acid hydrolysis of the various glycosidic and phosphodiester bonds in these polysaccharides, with evidence to suggest that the acid lability of a given bond can be dramatically different from one polysaccharide to another.

Structural studies of a rhamnogalacturonan from the stipules of Musanga cercropoides

The major water-soluble polysaccharide isolated from the stipules of Musanga cercropoides has been investigated, using n.m.r. spectroscopy, methylation analysis, and solvolysis in liquid hydrogen fluoride as the main methods. It is concluded that the polysaccharide is of the rhamnogalacturonan type and is, at least mainly, composed of tetrasaccharide repeating-units having the following structure [formula: see text] The polysaccharide further contains approximately two O-acetyl groups per repeating unit, which have not been located.