Dependence of 13C chemical shifts on the spatial interaction of protons, and its application in structural and conformational studies of oligo- and poly-saccharides

Structure, Physicochemical Properties and Biological Activity of Lipopolysaccharide from the Rhizospheric Bacterium Ochrobactrum quorumnocens T1Kr02, Containing d-Fucose Residues

Lipopolysaccharides (LPSs) are major components of the outer membranes of Gram-negative bacteria. In this work, the structure of the O-polysaccharide of Ochrobactrum quorumnocens T1Kr02 was identified by nuclear magnetic resonance (NMR), and the physical-chemical properties and biological activity of LPS were also investigated. The NMR analysis showed that the O-polysaccharide has the following structure: →2)-β-d-Fucf-(1→3)-β-d-Fucp-(1→. The structure of the periplasmic glucan coextracted with LPS was established by NMR spectroscopy and chemical methods: →2)-β-d-Glcp-(1→. Non-stoichiometric modifications were identified in both polysaccharides: 50% of d-fucofuranose residues at position 3 were O-acetylated, and 15% of d-Glcp residues at position 6 were linked with succinate. This is the first report of a polysaccharide containing both d-fucopyranose and d-fucofuranose residues. The fatty acid analysis of the LPS showed the prevalence of 3-hydroxytetradecanoic, hexadecenoic, octadecenoic, lactobacillic, and 27-hydroxyoctacosanoic acids. The dynamic light scattering demonstrated that LPS (in an aqueous solution) formed supramolecular particles with a size of 72.2 nm and a zeta-potential of -21.5 mV. The LPS solution (10 mkg/mL) promoted the growth of potato microplants under in vitro conditions. Thus, LPS of O. quorumnocens T1Kr02 can be recommended as a promoter for plants and as a source of biotechnological production of d-fucose.

Structure of the O-specific polysaccharide of Ochrobactrum endophyticum KCTC 42485T containing 3-(3-hydroxy-2,3-dimethyl-5-oxoprolyl)amino-3,6-dideoxy-d-galactose

Ochrobactrum endophyticum (syn. Brucella endophytica) is an aerobic species of Alphaproteobacteria isolated from healthy roots of Glycyrrhiza uralensis. Here we report the structure of the O-specific polysaccharide obtained by mild acid hydrolysis of the lipopolysaccharide of the type strain KCTC 42485:→3)-α-l-FucpNAc-(1→3)-β-d-QuipNAc-(1→2)-β-d-Fucp3NAcyl-(1→ where Acyl is 3-hydroxy-2,3-dimethyl-5-oxoprolyl. The structure was elucidated using chemical analyses along with ¹H and ¹³C NMR spectroscopy (including ¹H,¹H COSY, TOCSY, ROESY and ¹H,¹³C HSQC, HMBC, HSQC-TOCSY and HSQC-NOESY experiments). To our knowledge the OPS structure is novel and has not been previously published.

Osteosaponins 1 and 2: two new saponin glycosides from Osteospermum vaillantii

Osteospermum vaillantii (Decne) T. Norl., collected from southern Saudi Arabia, yielded two new saponins characterised as 3-O-beta-D-glucopyranosyl-(2' --> 1'')-beta-D-glucopyranosyl-(3' --> 1''')-O-beta-D-galactopyranosyl-oleanolic acid, designated as osteosaponin, and 3-O-beta-D-glucopyranosyl-(2' --> 1'')-beta-D-glucopyranosyl-(2''-1''''')-beta-D-glucopyranosyl-(3' --> 1''')-O-beta-(-D-galactopyranosyl-oleanolic-acid-28-C(O)-O-beta-D-(1'''')-glucopyranosyl ester, designated as osteosaponin. The sugar attachments and configurations were confirmed by spectroscopic methods, that is, 1H, 13C-NMR, COSY, HSQC and HMBC-NMR experiments.

Escherichia coli O123 O antigen genes and polysaccharide structure are conserved in some Salmonella enterica serogroups

The serotyping of O and H antigens is an important first step in the characterization of Salmonella enterica. However, serotyping has become increasingly technically demanding and expensive to perform. We have therefore sequenced additional S. enterica O antigen gene clusters to provide information for the development of DNA-based serotyping methods. Three S. enterica isolates had O antigen gene clusters with homology to the Escherichia coli O123 O antigen region. O antigen clusters from two serogroup O58 S. enterica strains had approximately 85 % identity with the E. coli O123 O antigen region over their entire length, suggesting that these Salmonella and E. coli O antigen regions evolved from a common ancestor. The O antigen cluster of a Salmonella serogroup O41 isolate had a lower level of identity with E. coli O123 over only part of its O antigen DNA cluster sequence, suggesting a different and more complex evolution of this gene cluster than those in the O58 strains. A large part of the Salmonella O41 O antigen DNA cluster had very close identity with the O antigen cluster of an O62 strain. This region of DNA homology included the wzx and wzy genes. Therefore, molecular serotyping tests using only the O41 or O62 wzx and wzy genes would not differentiate between the two serogroups. The E. coli O123 O-antigenic polysaccharide and its repeating unit were characterized, and the chemical structure for E. coli O123 was entirely consistent with the O antigen gene cluster sequences of E. coli O123 and the Salmonella O58 isolates. An understanding of both the genetic and structural composition of Salmonella and E. coli O antigens is necessary for the development of novel molecular methods for serotyping these organisms.

Sequence determination of oligosaccharides and regular polysaccharides using NMR spectroscopy and a novel Web-based version of the computer program casper

A WWW-interface to a program for structure elucidation of oligo- and polysaccharides using NMR data, CASPER, is presented. The interface and the underlying program have been extensively tested using published data and it was able to simulate 13C NMR spectra of >200 structures with an average error of about 0.3 ppm/resonance. When applied to the repeating units of Escherichia coli O-antigens the published structures were found among the five highest ranked structures in 75% of the cases. The average deviation between calculated and experimental 13C chemical shifts was 0.45 ppm. Oligosaccharide spectra were calculated with even better accuracy (0.23 ppm/resonance) and the correct structure was ranked 1st or 2nd in all the cases examined. Additional NMR experiments that may be required to distinguish between candidate structures are aided by the assignments provided by the program. This computational approach is also suitable for use in structural confirmation of chemically or enzymatically synthesized oligosaccharides. The program is found at http://www.casper.organ.su.se/casper.

Revised structures for the capsular polysaccharides from Staphylococcus aureus Types 5 and 8, components of novel glycoconjugate vaccines

Glycoconjugate vaccines based on the capsular polysaccharides (CPSs) from Staphylococcus aureus serotypes 5 and 8 conjugated to genetically detoxified recombinant exoprotein A (rEPA) from Pseudomonas aeruginosa have been shown, in Phase 3 clinical trials, to elicit a strong bactericidal immune response in end-stage renal disease patients. Such vaccines have the potential to reduce morbidity and mortality due to methicillin-resistant Staphylococcus aureus (MRSA), a major cause of hospital-acquired infection. The serotype 5 and 8 polysaccharides have been fully characterized by NMR spectroscopy and full structural analyses carried out. Published structures were found incorrect and the revised structures of the repeat units of the two polysaccharides are: [carbohydrate structure: see text]. Resonances indicative of the presence of peptidoglycan were observed in the spectra of both CPSs, consistent with reports that the CPS is covalently linked to peptidoglycan.

Confirmation of the D configuration of the 2-substituted arabinitol 1-phosphate residue in the capsular polysaccharide from Streptococcus pneumoniae Type 17F

The absolute configuration of the 2-substituted arabinitol 1-phosphate residue present in the repeating unit of the capsular polysaccharide (CPS) from Streptococcus pneumoniae Type 17F is confirmed as D, based on a comparison of proton and carbon chemical shifts in a synthetic oligosaccharide and in an oligosaccharide derived from the CPS by degradation.

The structure of a complex glycosylphosphatidyl inositol-anchored glucoxylan from the kinetoplastid protozoan Leptomonas samueli

The structure of a glycosylphosphatidyl inositol-anchored glucoxylan (GPI-glucoxylan) synthesized by the monogenetic trypanosomatid Leptomonas samueli has been determined. The glucoxylan is anchored to the membrane by phytoceramide and an oligosaccharide core, the structure of which is identical to glycoinositolphospholipids (GIPLs) expressed by this protozoan. The glucoxylan chain is linear, containing -->4Glcalpha1-->, -->4Xylbeta1--> and -->3Xylbeta1--> residues. A well defined sequence heterogeneity was analysed in terms of a series of overlapping trisaccharide substructures. A proportion of the chains are capped with a GlcAalpha1-->3Glcalpha1--> sequence. While an average GlcA-capped chain contained 10 Glc and 16 Xyl residues, uncapped chains have a higher molecular mass with an average of 30 Glc and 50 Xyl per chain. We propose a mode of biosynthesis based on the observed structural heterogeneity.

Structure determination of the O-antigenic polysaccharide from the enteroinvasive Escherichia coli O136

The structure of the O-antigen polysaccharide of the lipopolysaccharide from the enteroinvasive Escherichia coli O136 has been elucidated. The composition of the repeating unit was established by sugar and methylation analysis together with 1H and 13C NMR spectroscopy. Two-dimensional nuclear Overhauser effect spectroscopy (NOESY) and heteronuclear multiple-bond correlation experiments were used to deduce the sequence. The absolute configuration for the nonulosonic acid (NonA) could be determined using spin-spin coupling constants, 13C chemical shifts and NOESY. The anomeric configuration of the NonA was determined via vicinal and geminal 13C,1H coupling constants. The structure of the repeating unit of the polysaccharide from E. coli O136 is as follows, in which beta-NonpA is 5,7-diacetamido-3,5,7, 9-tetradeoxy-Lglycero-beta-Lmanno-nonulosonic acid: -->4)-beta-NonpA-(2-->4)-beta-D-Galp-(1-->4)-beta-D-GlcpNAc-(1-->

Somatic antigens of pseudomonads: structure of the O-specific polysaccharide of Pseudomonas fluorescens biovar B, strain IMV 247

The O-specific polysaccharide of Pseudomonas fluorescens biovar B, strain IMV 247, was studied by acid hydrolysis, GLC-MS and 1H and 13C NMR spectroscopy, including 1D and 2D NOE, 2D hybrid TOCSY and ROESY (TORO), and 2D H-detected heteronuclear multiple-bond correlation (HMBC) experiments. The polysaccharide was found to contain L-rhamnose, 3.6-dideoxy-3-[(S)-3-hydroxybutyramido]-D-glucose (D-Qui3NHb), 2-acetamido- 2,4,6-trideoxy-4-[(S)-3-hydroxybutyramido-D-glucose (D-QuiNAc4NHb) and 2-acetamido-2- deoxy-D-galacturonic acid (D-GalNAcA). Partial acid hydrolysis of the polysaccharide resulted in a non-reducing GalNAcA-->QuiNAc4NHb disaccharide with the 3-hydroxybutyryl group glycosylated intramolecularly by the QuiN4N residue. The following structure of the tetrasaccharide repeating unit of the polysaccharide was established:-->4) -alpha-D-GalpNAcA-(1-->3)- alpha-D-QuipNAc4NHb-(1-->2)-beta-D-Quip3NHb-(1-->2)-alpha-L- Rhap(1-->.

Structural studies on the Shigella-like Escherichia coli O121 O-specific polysaccharide

The O-specific polysaccharide isolated from the lipopolysaccharide (LPS) of Escherichia coli O121 by mild acid hydrolysis has been studied using mainly NMR spectroscopy. The polysaccharide was treated with mild base to yield a O-deacetylated polysaccharide which contained D-GlcNAc, D-GalNAcA, D-GalNAcAN (2-acetamido-2-deoxy-D-galacturonamide) and D-Qui4NAcGly (where D-Qui4N is 4-amino-4,6-dideoxy-D-glucose) in equimolar proportions. The presence of the amide was confirmed by recording the 1H NMR spectrum of the O-deacetylated polysaccharide at different pH values. The O-acetyl group was located on O-3 of the GalNAcAN and the structure of the polysaccharide can be written as [sequence: see text] This structure is almost identical to that previously reported for the O-specific polysaccharide of Shigella dysenteriae type 7 LPS, the only difference being that O-acetylation is stoichiometric in the latter.

Synthesis of alpha- and beta-linked tyvelose epitopes of the Trichinella spiralis glycan: 2-acetamido-2-deoxy-3-O-(3,6-dideoxy-D-arabino-hexopyranosyl)-beta -D-galactopyranosides

The anomeric configuration of tyvelose, 3,6-dideoxy-D-arabino-hexopyranose, in the recently discovered glycan epitopes of the parasite Trichinella spiralis has not been established. Two 2-(trimethylsilyl)ethyl disaccharide glycosides, alpha- and beta-Tyv-(1-->3)-beta-D-GalNAc (4 and 5), have been synthesized to provide model compounds that, together with the methyl 3,6-dideoxy-alpha- and beta-D-arabino-hexopyranosides (2 and 3), aid the determination of the anomeric configuration of tyvelose residues in the parasite glycan, either indirectly by immunochemical inhibition data or directly by the technique of 1H NMR spectroscopy. Methyl 3,6-dideoxy-beta-D-arabino-hexopyranoside (3) was synthesized from methyl 2,3-anhydro-4,6-O-benzylidene-beta-D-mannopyranoside (9) by a method previously used for the alpha anomer 2. Benzylation of 2 provided a route to the glycosyl donor, 2,4-di-O-benzyl-3,6-dideoxy-alpha-D-arabino-hexopyranosyl chloride (30), that reacted with the selectively protected 2-acetamido-2-deoxy-D-galactopyranoside alcohol 18 in the presence of an insoluble silver zeolite catalyst to give the alpha- and beta-linked disaccharides 31 and 32. Glycosylation of the related 2-acetamido-2-deoxy-D-galactopyranoside alcohol 27 by 30 under similar conditions provided disaccharides 33 and 34 containing a tether. Deprotection of the saccharide and derivatization of the tether with 1,2-diaminoethane provided amide derivatives 35 and 36 suitable for the preparation of neoglycoconjugate antigens. Complete 1H and 13C NMR chemical shifts of the deprotected disaccharides and monosaccharides are reported.

Similarity of "core" structures in two different glycans of tyrosine-linked eubacterial S-layer glycoproteins

Previously, the repeating-unit structure of the S-layer glycoprotein from the eubacterium Bacillus alvei CCM 2051 has been determined to be [-->3)-beta-D-Galp-(1-->4)-[alpha-D-Glcp-(1-->6)-]-beta-D-ManpNAc- (1-->]n (E. Altman, J.-R. Brisson, P. Messner, and U. B. Sleytr, Biochem. Cell Biol. 69:72-78, 1991). Nuclear magnetic resonance spectroscopic reexamination of this glycan reveals that the O-antigen-like domain of the polysaccharide is [see text] connected with the S-layer polypeptide through the "core" structure -->3)-alpha-L-Rhap-(1-->3)-alpha-L-Rhap-(1-->3)-alpha-L-R hap-(1-->3)-beta-D-Galp-(1-->O)-Tyr. Except for the substitution in position 4 of the nonreducing rhamnose with the modified glyceric acid phosphate residue GroA-2-->OPO2-->4-beta-D-ManpNAc-(1-->, this core is identical to the core of the tyrosine-linked glycan from the S-layer glycoprotein of Thermoanaerobacter thermohydrosulfuricus L111-69 (K. Bock, J. Schuster-Kolbe, E. Altman, G. Allmaier, B. Stahl, R. Christian, U. B. Sleytr, and P. Messner, J. Biol. Chem. 269:7137-7144, 1994).

Molecular recognition of antigenic polysaccharides: a conformational comparison of capsules from Streptococcus pneumoniae serogroup 9

Aqueous solution conformations of three antigenic bacterial capsular polysaccharides (CPS) from S. pneumoniae serogroup 9 were determined using a combination of NMR data (NOE build-up rates and conformation-dependent chemical shifts), simulated annealing, and molecular dynamics simulations. Each polymer adopts a flexible extended ribbon conformation in solution. Conformations of structural elements shared by each PS are indistinguishable. Differences in conformations are minor and localised at the sites of structural variations; there is no evidence of long-range stabilisation of a secondary structure. It is likely that antigenic specificity of Group 9 PS is dominated by local structural variation rather than by conformational differences.

Conformational equilibria of 4-thiomaltose and nitrogen analogues of maltose in aqueous solutions

The 1H and 13C NMR data at neutral pH are presented for methyl 4-thio-beta- and alpha-maltoside (1 and 2) together with methyl 1-thio-alpha-D-glucopyranoside (3) and methyl 4-thio-alpha-D-glucopyranoside (4) as reference compounds. Furthermore, the NMR data at high and low pH are presented for the 4-amino-4-deoxy analogues of methyl alpha-maltoside (5 and 6) and the 5-amino-5-deoxy analogue (8) together with reference compounds methyl 4-amino-4-deoxy-alpha-D-glucopyranoside (7) and 1-deoxynojirimycin (9). The experimental NMR data are assigned by 1- and 2-dimensional spectroscopy at 500 and 600 MHz. The conformational preferences of the maltose analogues 1, 2, 5, 6 and 8 are evaluated by difference NOE experiments, 13C-1H long-range coupling constants, chemical-shift comparison with model compounds and hard-sphere force field calculations for 1 using Monte Carlo simulations. Additionally, the results are compared with extensive experimental NOE data for methyl alpha- and beta-maltoside and the results discussed in light of earlier studies.

An NMR spectroscopic and conformational study of 12 pseudo-disaccharides (D-glucopyranosyl-5a-carba-D- and -L-glucopyranoses)

NMR spectroscopic data for 12 pseudo-disaccharides of the general structure: (alpha or beta)-D-glucopyranosyl-(1-->chi)-5a-carba-(D or L)-glucopyranose, representing analogues of laminaribiose (beta-D-Glc p, chi = 3), cellobiose (beta-D-Glc p, chi = 4), and maltose (alpha-D-Glc p, chi = 4) are presented. The assigned NMR chemical shifts together with NOE difference measurements in association with calculations applying the HSEA force field combined with Monte Carlo simulations have been used to assess the conformational preferences of the investigated compounds. The results are correlated with general structural features involved in the interactions between monosaccharide units of oligosaccharides.

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.

Complete structure of the tyrosine-linked saccharide moiety from the surface layer glycoprotein of Clostridium thermohydrosulfuricum S102-70

In this study, we have extended and completed a previous investigation (P. Messner, R. Christian, J. Kolbe, G. Schulz, and U. B. Sleytr, J. Bacteriol. 174:2236-2240, 1992) in which we demonstrated for the first time in prokaryotic organisms the presence of a novel O-glycosidic linkage via tyrosine. The surface layer glycoprotein of the eubacterium Clostridium thermohydrosulfuricum S102-70 is arranged in a hexagonal lattice, with center-to-center spacings of approximately 16.3 nm. Molecular weight determination by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of both glycosylated and chemically deglycosylated surface layer glycoprotein showed values for the monomeric subunits of 94,000 and 87,500, respectively. Glycopeptide fractions obtained after exhaustive pronase digestion of purified, intact glycoprotein were isolated by reversed-phase liquid chromatography. One- and two-dimensional nuclear magnetic resonance studies, together with chemical analyses and plasma desorption time-of-flight mass spectrometry, were used to elucidate the structure of the hexasaccharide moiety linked by the novel O-glycosidic linkage to tyrosine. The combined evidence suggests the following structure: beta-D-Galf-(1-->3)-alpha-D-Galp- (1-->2)-alpha-L-Rhap-(1-->3)-alpha-D-Manp-(1--3)-alpha-L- Rhap-(1-->3)-beta- D-Glcp-(1-->4)-L-Tyr.

NMR spectroscopy in the structural elucidation of oligosaccharides and glycosides

The potential of one- and two-dimensional NMR techniques for the identification of individual sugar residues, their anomeric configuration, interglycosidic linkages, sequencing and the site of any appended group, in establishing the structures of naturally occurring oligosaccharides and glycosides is presented.

Analysis of a novel linkage unit of O-linked carbohydrates from the crystalline surface layer glycoprotein of Clostridium thermohydrosulfuricum S102-70

The surface layer glycoprotein of Clostridium thermohydrosulfuricum S102-70 was shown to contain a new type of glycan chain. Different from all known eubacterial glycoproteins, the saccharide moiety consists only of six sugar residues without any repeat sequences. Proteolytic digestion of purified S-layer glycoprotein resulted in isolation of several glycopeptide fractions. These are composed of the same hexasaccharide portion but are linked to oligopeptides of different length. One of them contains only a single amino acid. As concluded from chemical analyses and proton and carbon nuclear magnetic resonance spectroscopy of this preparation, the hexasaccharide moiety is linked via a novel O-glycosidic linkage. This is a beta-D-glucose residue linked to the phenolic hydroxyl group of tyrosine in intact S-layer glycoprotein.

N.m.r. and conformational analysis of the capsular polysaccharide from Streptococcus pneumoniae type 4

The 1H- and 13C-n.m.r. data on the capsular polysaccharide (1) produced by Streptococcus pneumoniae type 4, the depyruvated polysaccharide (2), and a tetrasaccharide (3a) derived by Smith degradation of 2 were used as constraints on a computer-generated model of the conformation of 1 and to assess the effects of the pyruvic acetal substituent on the conformation. The dynamics of the polysaccharide systems and the influence of the pyruvic acetal were investigated using 13C-n.m.r. relaxation measurements.

A nuclear magnetic resonance spectroscopic and conformational study of eight pseudo-trehaloses (D-glucopyranosyl 5a-carba-D- and -L-glucopyranosides)

N.m.r. data (1H and 13C) are presented for eight pseudo-trehalose derivatives in which the D-glucopyranosyl moiety is alpha or beta and the 5a-carbaglucopyranoside moiety is alpha-D, beta-D, alpha-L, or beta-L. The differences in the chemical shifts and then n.O.e. effects have been correlated with the preferred conformations estimated from empirical force-field calculations (HSEA), which have been used to calculate the average parameters over the whole energy surface. Of the four alpha-D-glucopyranosyl derivatives, only that with a 5a-carba-beta-D-glucopyranoside moiety (3) was a substrate for glucoamylase.

Solution behavior of methyl beta-xylobioside: conformational flexibility revealed by n.m.r. measurements and theoretical calculations

The conformations of methyl beta-xylobioside in solution have been determined by n.m.r. spectroscopy. Interglycosidic 3JC,H values and the chemical shifts of the 13C resonances were measured at various temperatures in the range 238-378 K for solutions in 1,4-dioxane, methanol, methyl sulfoxide, and water. The temperature and solvent dependencies of the data obtained suggest conformational flexibility. Quantum-chemical PCILO calculations, with evaluation of the solvent effects, and molecular mechanics calculations revealed the existence of 7 low-energy regions for which the geometries and energies were determined. The computed abundances of conformers and averaged J values accord with the experimental data.

Characterization of the surface layer glycoprotein of Clostridium symbiosum HB25

The cell surface of Clostridium symbiosum HB25 is covered by a squarely arranged surface layer (S-layer) glycoprotein. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the sodium dodecyl sulfate-soluble whole-cell extract showed the presence of several high-molecular-weight protein bands in a narrow range (approximate Mr, 140,000) which, upon periodic acid-Schiff staining, gave a positive reaction. After proteolytic degradation of the purified S-layer glycoprotein, a single glycopeptide fraction was obtained by gel permeation chromatography. Hydrolysis, treatment with aqueous hydrofluoric acid, and 1H and 13C nuclear magnetic resonance studies showed that the glycoprotein glycan is a high-molecular-weight polymer (approximate Mr, 15,000) of tetrasaccharide repeating units with the component sugars N-acetylgalactosamine (GalNAc), N-acetylmannosamine (ManNAc), and N-acetylbacillosamine (BacNAc; 2-N-acetyl-4-amino-2,4,6-trideoxy glucose) linked by monophosphate diesters. The following structure is proposed: [----6)-alpha-D-ManpNAc-(1----4)-beta-D-GalpNAc-(1----3)-alpha-D-+ ++BacpNAc- (1----4)-alpha-D-GalpNAc-(1----PO3)----]n. The nuclear magnetic resonance data provided evidence for a charge interaction between the free amino group of BacNAc and the phosphate group of adjacent glycan chains. Since polycationic ferritin did not label the cell surface of intact cells, an electrostatic interaction can also be expected in vivo, leading to a charge-neutral outer surface, which is characteristic of all other S layers from members of the family Bacillaceae studied so far.

The use of bacteriophage-mediated depolymerisation in investigations of the structure of the capsular polysaccharide from Klebsiella serotype K71

The structure (1) of the heptasaccharide repeating-unit of the capsular polysaccharide from Klebsiella serotype K71 follows from methylation analysis and n.m.r. and mass-spectrometric studies of the oligosaccharides obtained on depolymerisation of the polysaccharide with a bacteriophage-borne endo-rhamnosidase. [formula; see text].

Structure of the O-specific polysaccharide from Enterobacter cloacae strain N.C.T.C. 11579 (serogroup O10)

The O-specific polysaccharide from the reference strain (N.C.T.C. 11579) for Enterobacter cloacae serogroup O10 has been isolated and characterised. By means of n.m.r. spectroscopy and methylation analysis, and by studies of the products obtained by Smith degradation or by N-deacetylation-deamination, the repeating unit of the polysaccharide could be allocated the structure shown. The polysaccharides from two cross-reacting serogroups (O9 and O11) have the same monosaccharide composition. (Formula: see text)

Structural studies of the O-antigenic polysaccharide of Escherichia coli O86, which possesses blood-group B activity

The O-specific side-chains of the lipopolysaccharide from Escherichia coli O86:K2:H2 have been investigated using n.m.r. spectroscopy, methylation analysis, and specific degradations, and shown to be composed of the pentasaccharide repeating-unit (formula; see text) which represents the biological repeating-unit. The blood-group B activity was confirmed by an enzyme-linked immunosorbent assay.

Structural studies of the capsular polysaccharide from Streptococcus pneumoniae type 2, a reinvestigation

The structure of the capsular polysaccharide from Streptococcus pneumoniae type 2 has been reinvestigated, specific degradations and n.m.r. spectroscopy being the main methods used. It is concluded that the polysaccharide is composed of hexasaccharide repeating-units having the following structure, which differs from that previously proposed. formula; see text)

Somatic antigens of Shigella: structure of the O-specific polysaccharide chain of the Shigella dysenteriae type 7 lipopolysaccharide

4-(N-Acetylglycyl)amino-4,6-dideoxy-D-glucose has been identified as a component of the Shigella dysenteriae type 7 O-specific polysaccharide, in addition to the previously reported 2-acetamido-2-deoxy-D-glucose and 2-acetamido-2-deoxy-D-galacturonic acid. On the basis of selective cleavage with anhydrous hydrogen fluoride and analysis by 1H- and 13C-n.m.r. spectroscopy and f.a.b.-mass spectrometry, it was concluded that the tetrasaccharide repeating-unit of the polysaccharide has the following structure: (structure; see text) where D-GalNAcAN is 2-acetamido-2-deoxy-D-galacturonamide and D-Qui4N is 4-amino-4,6-dideoxy-D-glucose.

A computer-assisted structural analysis of regular polysaccharides on the basis of 13C-n.m.r. data

A computerised approach to the structural analysis of unbranched regular polysaccharides is described, which is based on an evaluation of the 13C-n.m.r. spectra for all possible primary structures within the additive scheme starting from the chemical shifts of the 13C resonances of the constituent monosaccharides and the average values of the glycosylation effects. The analysis reveals a structure (or structures), the evaluated spectrum of which resembles most closely that observed. The approach has been verified by using a series of bacterial polysaccharides of known structure and, in combination with methylation analysis data, for the determination of the presently unknown structures of the O-specific polysaccharides from Salmonella arizonae O59 and O63, and Proteus hauseri O19.

Isolation and structure determination of a diacetamidodideoxyuronic acid-containing glycan chain from the S-layer glycoprotein of Bacillus stearothermophilus NRS 2004/3a

A glycan isolated from the surface-layer glycoprotein of Bacillus stearothermophilus strain NRS 2004/3a was shown by 1H- and 13C-n.m.r. spectroscopy to have the tetrasaccharide repeating-unit ----4)-beta-ManpA2,3(NAc)2-(1----3)-alpha-GlcpNAc-(1----4)-beta- ManpA2,3(NAc)-(1----6)-alpha-Glcp(1----.

Somatic antigens of Pseudomonas aeruginosa. The structure of O-specific polysaccharide chains of lipopolysaccharides of P. aeruginosa O3 (Lányi), O25 (Wokatsch) and Fisher immunotypes 3 and 7

O-specific polysaccharides, obtained on mild acid degradation of lipopolysacchrides of the serologically related strains Pseudomonas aeruginosa O3 (Lányi classification), O25 (Wokatsch classification) and immunotypes 3 and 7 (Fisher classification), are built up of trisaccharide repeating units involving 2-acetamido-2,6-dideoxy-D-galactose (N-acetyl-D-fucosamine), 2,3-diacetamido-2,3-dideoxy-D-mannuronic acid or 2,3-diacetamido-2,3-dideoxy-L-guluronic acid and 3-acetamidino-2-acetamido-2,3-dideoxy-D-mannuronic acid or 3-acetamidino-2-acetamido-2,3-dideoxy-L-guluronic acid. Lányi O3(a),3d,3f and Wokatsch O25 polysaccharides contain also O-acetyl groups. On the basis of solvolysis with anhydrous hydrogen fluoride, resulting in trisaccharide fragments with N-acetylfucosamine residue at the reducing terminus, chemical modifications of the acetamidino group (alkaline hydrolysis to the acetamido group or reductive deamination to the ethylamino group), as well as analysis by 1H-NMR (including nuclear Overhauser effect experiments) and 13C-NMR spectroscopy, and fast-atom bombardment mass spectrometry, it was concluded that the repeating units of the polysaccharides have the following structures: (Formula: see text) where HexNAcAmA = alpha-L-GulNAcAmA (approximately 70%) or beta-D-ManNacAMA (approximately 30%). Lányi O3(a),3d,3f polysaccharide involves two types of repeating units, which differ from each other only in the configuration at C-5 of the 3-acetamidino-2-acetamido-2,3-dideoxyuronic acid residue. Lányi O3(a),3c,O3a,3d,3e and Fisher immunotypes 3 and 7 polysaccharides contain, together with the major repeating units shown above, a small proportion of units in which the derivative of alpha-L-guluronic acid is replaced by the corresponding beta-D-manno isomer. The data obtained provide the opportunity to substantiate the serological interrelations between these strains of P. aeruginosa by the presence in the O-specific polysaccharides of common monosaccharides or disaccharide fragments. The distinctions between them stem from the presence or absence of the O-acetyl group, a different configuration of the glycosidic linkage of the N-acetylfucosamine residue and/or a different configuration at C-5 of one or both derivatives of diaminouronic acids.