PubMed Health⌕ Search

Biomedical subjects

G Widmalm

Publications and source records attributed to G Widmalm.

At least 37 records · Page 2Linked to original sources
PubMed2000

Modified GOESY in the analysis of disaccharide conformation.

One-dimensional nuclear magnetic resonance techniques were applied to the conformational investigation of a disaccharide. More specifically, nuclear Overhauser enhancements (NOEs) of protons on either side of the glycosidic bond have been used to determine the conformation of the disaccharide alpha-l-Rhap-(1 --> 2)-alpha-l-Rhap-OMe. A modified GOESY sequence, incorporating selective excitation and pulsed field gradient enhancement, was developed and used to accurately measure small NOE signals of interest. These experiments were named M-GOESY, for modified GOESY, and the data they provided were used to calculate internuclear distances in the disaccharide molecule. The accuracy of the M-GOESY measurements was enhanced by elimination of indirect effects, or spin diffusion, by selective inversion(s) of either the intermediate magnetization or the source and target magnetization during the mixing time. Results of this study indicate that the alpha-l-Rhap-(1 --> 2)-alpha-l-Rhap-OMe disaccharide molecule exists primarily in one conformation, with the glycosidic torsion angle psi approximately -30 degrees based on past molecular dynamics simulations.

Disaccharides↗
PubMed1999

A conformational study of the vicinally branched trisaccharide beta-D-glcp-(1 --> 2)[beta-D-glcp-(1 --> 3)]alpha-D-Manp-OMe by nuclear Overhauser effect spectroscopy (NOESY) and transverse rotating-frame Overhauser effect spectroscopy (TROESY) experiments: comparison to Monte Carlo and Langevin dynamics simulations.

The trisaccharide beta-D-Glcp-(1 --> 2)[beta-D-Glcp-(1 --> 3)]alpha-D-Manp-OMe, a model for branching regions in oligosaccharides, has been investigated by one-dimensional DPFGSE (1)H, (1)H nuclear Overhauser effect spectroscopy (NOESY) and transverse rotating-frame Overhauser effect spectroscopy (TROESY) experiments at 30 degrees C in water and in the solvent mixture water : dimethyl sulfoxide (7 : 3). Cross-relaxation rates were obtained from the nmr experiments and interpreted as proton-proton distances. From Metropolis Monte Carlo and Langevin dynamics simulations, distances were calculated and compared to those obtained from experiment. Using the previously determined dynamics from carbon-13 nmr relaxation measurements of the trisaccharide in the solvent mixture, intraresidue proton distances could be obtained that were in excellent to reasonable agreement with those calculated from simulations. In water, the isolated spin-pair approximation was used for comparison of interproton distances. The experimentally derived distances in both solvents showed that the trans-glycosidic distances were shorter between the anomeric proton of the glucosyl group and the proton at the linkage position, respectively, than to the proton on the adjacent carbon on the mannosyl residue. The interresidue distances calculated from the computer simulations, performed with three different force fields, namely HSEA, PARM22, and CHEAT95, resulted in the reverse order in all cases but one.

Carbohydrate Conformation↗
PubMed1999

Structural determination and biosynthetic studies of the O-antigenic polysaccharide from the enterohemorrhagic Escherichia coli O91 using 13C-enrichment and NMR spectroscopy.

The structure of the O-antigenic polysaccharide from the enterohemorrhagic Escherichia coli O91 has been determined using primarily NMR spectroscopy on the (13)C-enriched polysaccharide. The O-antigen is composed of pentasaccharide repeating units with the following structure: -->4)-beta-D-Galp-(1-->4)-beta-D-GlcpNAc-(1-->4)-beta-D-GlcpA-6-N- Gly -(1-->3)-beta-D-GlcpNAc-(1-->4)-alpha-D-Quip-3-N-[(R)-3-hydroxy butyra mido]-(1-->. The bacterium was grown with D-[UL-(13)C]glucose in the medium which resulted in an overall degree of labeling of approximately 65% in the sugar residues and approximately 50% in the N-acyl substituents, indicating some metabolic dilution in the latter. The (13)C-enrichment of the polysaccharide proved valuable since NMR assignments could be made on the basis of (13)C, (13)C-connectivity in uniformly labeled residues. The biosynthesis of the (R)-3-hydroxybutyramido substituent via C(2) fragments was identified by NMR spectroscopy. The (R)-configuration at C3 is in accord with fatty acid biosynthesis. Additional cultures with specifically labeled D-[1-(13)C]glucose or D-[6-(13)C]glucose corroborated the direct incorporation of glucose as the building block for the hexose skeletons in the polysaccharide and the biosynthesis of acyl substituents occurring via the triose pool followed by decarboxylation to give acetyl building blocks labeled with (13)C at the methyl group.

Acetylation↗
PubMed1999

Structural studies of the O-antigen polysaccharide from the enteroinvasive Escherichia coli O173.

The structure of the O-antigen polysaccharide (PS) from Escherichia coli O173 has been investigated. Sugar and methylation analyses, electrospray ionisation mass spectrometry together with 1H, 31P and 13C NMR spectroscopy were the main methods used. The structure of the pentasaccharide repeating unit of the PS was found to be: [formula: see text] By treatment with 48% HF the phosphoric diester linkage was cleaved together with the glycosidic linkage of the fucosyl group, rendering a tetrasaccharide with the structure: alpha-D-Glcp-(1-->2)-beta-D-Glcp-(1-->3)-beta-D-GlcpNAc-(1-->3)-D-Glc.

Animals↗
PubMed1999

Structure elucidation of the O-antigenic polysaccharide from the enteroaggregative Escherichia coli strain 62D1.

The O-antigen polysaccharide of the lipopolysaccharide from the enteroaggregative Escherichia coli strain 62D1 has been determined. Sugar and methylation analysis together with 1H and 13C NMR spectroscopy revealed the components of the repeating unit. Two-dimensional NOESY and heteronuclear multiple-bond correlation experiments were used to deduce the sequence. 1H and 13C NMR spectra indicate heterogeneity in the polysaccharide. Methylation analysis and 1H NMR spectra of native and Smith-degraded material show that the majority (65%) of the repeating units has the following structure: Minor resonances in the NMR spectra are consistent with the presence of repeating units which lack the alpha-d-Galp terminal residue (35%).

Carbohydrate Conformation↗
PubMed1999

Cell wall teichoic acids of Actinomadura viridis VKM Ac-1315T.

The cell walls of Actinomadura viridis contain poly(glycosylglycerol phosphate) chains of complex structure. On the basis of NMR spectroscopy of the polymer and glycosides thereof the following structural units were found: beta-D-Galp3Me-(1-->4)[beta-D-Glcp-(1-->6)]-beta-D-Galp-(1-->1)-++ +snGro (G1); beta-D-Galp-(1-->4)-beta-D-Galp-(1-->1)-snGro (G2); beta-D-Galp3Me-(1-->4)-beta-D-Galp-(1-->1)-snGro (G2a); beta-D-Galp-(1-->1)-snGro (G3); beta-D-Galp-(1-->1)[beta-D-Galp-(1-->2)]-snGro (G4); beta-D-Glcp-(1-->2)-snGro (G5). Glycosides G1, G2 and G3 were the predominant components of the teichoic acid: they formed the polymer chain via phosphodiester bonds involving C-3 of the glycerol residue and C-3 of the galactosyl residue which in turn glycosylates C-1 of the glycerol residue. Whether the different glycosides make up the one chain or whether there are several poly(glycosylglycerol phosphate) chains in the cell wall remains to be determined. It was suggested that the minor component G5 is located at the nonterminal end of the chains. Compound G4 which contains disubstituted glycerol residues (unusual for the teichoic acid) was also found as a minor component; this may be the glycoside of a new type of teichoic acid, or a glycoside on the terminal end of the above mentioned chains. In addition, small amounts of 1,3-poly(glycerol phosphate) chains were found in the cell wall.

Actinomycetales↗
PubMed1999

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-->

Carbohydrate Conformation↗
PubMed1999

The lipopolysaccharide of moraxella catarrhalis structural relationships and antigenic properties.

Moraxella catarrhalis has recently been shown to be both widespread and pathogenic, in contrast to previous reports. Several factors have been suggested as virulence factors, lipopolysaccharide (LPS) being one. Recent studies have shown the LPS to be without the O-chain, i.e. the polysaccharide part, and to have specific structural features corresponding to each of the three serogroups, A, B and C. The structures resemble in many respects those present in other Gram-negative nonenteric bacteria, with a galabiosyl element as a prominent common denominator. The presence of such common structures suggests that the LPS of these bacteria might be a part of a mechanism of survival for bacteria colonizing the human host.

Antigens, Bacterial↗
PubMed1999

Structural studies on lipopolysaccharides of serologically non-typable strains of Helicobacter pylori, AF1 and 007, expressing Lewis antigenic determinants.

In contrast to other Helicobacter pylori strains, which have serologically detectable Lewis(x)+ (Le(x)) and Lewis(y)++ (++Le(y)) antigenic determinants in the O-specific polysaccharide chains of the lipopolysaccharides, H. pylori AF1 and 007 were non-typable with anti-Le(x) and anti-Le(y) antibodies. The carbohydrate portions of the lipopolysaccharides were liberated by mild acid hydrolysis and subsequently studied by sugar and methylation analyses, 1H-NMR spectroscopy and electrospray ionization-mass spectrometry. Compared with each other, and with lipopolysaccharides of strains studied previously, the lipopolysaccharides of both AF1 and 007 showed similarities, but also differences, in the structures of the core region and O-specific polysaccharide chains. The O-specific polysaccharide chains of both strains consisted of a short or long polyfucosylated poly-N-acetyl-beta-lactosamine chains, which were distinguished from those of other strains by a high degree of fucosylation producing a polymeric Le(x)chain terminating with Le(x) or Le(y) units:[sequence: see text] where n = 0 or 1 in strain AF1 and 0 in strain 007, m = 0-2, 6-7 in strain AF1 and m = 0-2, 6-7 or approximately 40 in strain 007, the medium-size species being predominant. Therefore, compared with other strains, the lack of reactivity of lipopolysaccharide of H. pylori AF1 and 007 with anti-Le(x) and anti-Le(y) may reflect the presence of a polymeric Le(x) chain and has important implications for serological and pathogenesis studies. As the substitution pattern of a D-glycero-D-manno-heptose residue in the outer core varied in the two strains, and an extended DD-heptan chain was present in some lipopolysaccharide species but not in others, this region was less conservative than the inner core region. The inner core L-glycero-D-manno-heptose region of both strains carried a 2-aminoethyl phosphate group, rather than a phosphate group, as reported previously for other H. pylori strains.

Antigens, Bacterial↗
PubMed1999

Structural elucidation of the O-antigenic polysaccharides from Escherichia coli O21 and the enteroaggregative Escherichia coli strain 105.

The structure of the O-antigen polysaccharide of the lipopolysaccharide from an enteroaggregative Escherichia coli (strain 105) has been elucidated, using primarily one-dimensional and two-dimensional NMR experiments. The sequence of residues was deduced with heteronuclear multiple-bond correlation and NOESY experiments. The structure of the repeating unit of the polysaccharide from the enteroaggregative E. coli is as follows:[sequence: see text] The structure of the O-antigen from enteroaggregative E. coli strain 105 was shown to be identical with that of E. coli O21 by sugar and methylation analyses as well as by 1H-NMR and 13C-NMR spectroscopy.

Bacterial Adhesion↗
PubMed1999

Structural studies utilizing 13C-enrichment of the O-antigen polysaccharide from the enterotoxigenic Escherichia coli O159 cross-reacting with Shigella dysenteriae type 4.

The structure of the O-antigen polysaccharide from Escherichia coli O159 has been determined using primarily NMR spectroscopy of the 13C-enriched polysaccharide. The sequence of the sugar residues could be determined by heteronuclear multiple bond connectivity NMR experiments. The polysaccharide is composed of a pentasaccharide repeating unit with the following structure: [sequence: see text] Matrix assisted laser desorption ionization mass spectrometry was performed on intact lipopolysaccharide and from the resulting molecular mass the O-antigen part was estimated to contain approximately 23 repeating units. Cross-reactivity of this O-antigen to that of Shigella dysenteriae type 4 was confirmed using enzyme-linked immunoabsorbant assay.

Adult↗
PubMed1999

Structural studies of the O-antigen polysaccharide from the enteroinvasive Escherichia coli O164 cross-reacting with Shigella dysenteriae type 3.

The structure of the O-antigen polysaccharide from Escherichia coli O164 has been determined. Nuclear magnetic resonance spectroscopy together with component and methylation analyses of lipid free polysaccharide were the principal methods used. The sequence of the sugar residues could be determined by NOESY and heteronuclear multiple bond connectivity NMR experiments. It is concluded that the polysaccharide is composed of a pentasaccharide repeating unit with the following structure: [structure: see text]. Matrix assisted laser desorption ionization mass spectrometry (MALDI-MS) was performed on intact lipopolysaccharide and from the resulting molecular mass, the O-antigen part was estimated to contain approximately 24 repeating units. The nature of the previously reported cross-reactivity of this O-antigen to those of Escherichia coli O124 and Shigella dysenteriae type 3 is discussed.

Animals↗
PubMed1998

Structural determination of the O-antigenic polysaccharide from Escherichia coli O35 and cross-reactivity to Salmonella arizonae O62.

The structure of the O-antigenic polysaccharide from Escherichia coli O35 has been investigated with the aid of NMR spectroscopy, sugar and methylation analyses. The sequence of the sugar residues could be determined by NOESY and heteronuclear-multiple-bond-connectivity NMR experiments. The polysaccharide is composed of hexasaccharide repeating units with the following structure, where Rha and GalNAcAN represent rhamnose and 2-acetamido-2-deoxy-galacturonamide, respectively: carbohydrate sequence [see text]. The O-antigen of Escherichia coli O35 is similar to the O-specific polysaccharide from Salmonella arizonae O62, which instead has a terminal 2-acetamido-2-deoxy-alpha-D-galacturonic acid residue. Immunochemical analyses using a rabbit antiserum specific for the Salmonella arizonae O62 O-antigen showed an identical reactivity with both lipopolysaccharides.

Carbohydrate Sequence↗
PubMed1998

Structural studies of the O-antigenic polysaccharide from Escherichia coli O139.

The structure of the O-antigenic polysaccharide from Escherichia coli O139 has been investigated with the aid of NMR spectroscopy, and sugar and methylation analyses. The sequence of the sugar residues was determined by NOESY and heteronuclear-multiple-bond-connectivity NMR experiments. The polysaccharide is composed of heptasaccharide repeating units containing 0.6 mol O-acetyl groups/repeating unit. The following structure is concluded, where Rha represents rhamnose. [structure in text]

Acetylation↗
PubMed1998

Structural determination of the O-antigenic polysaccharide from Escherichia coli O141.

The structure of the O-antigenic polysaccharide from Escherichia coli O141 has been determined. NMR spectroscopy and sugar and methylation analyses were the principal methods used. The sequence of the sugar residues could be determined by NOESY and heteronuclear multiple-bond connectivity (HMBC-) NMR experiments. The polysaccharide is composed of pentasaccharide repeating units with 1 O-acetyl group/repeating unit. The following structure, where Rha is 6-deoxymannose is concluded: carbohydrate sequence [see text].

Animals↗
PubMed1998

Structure and cross-reactivity of the O-specific polysaccharide of Proteus penneri strain 26, another neutral Proteus O-antigen containing 2-acetamido-2,6-dideoxy-L-glucose (N-acetyl-L-quinovosamine).

A neutral O-specific polysaccharide obtained from the lipopolysaccharide of Proteus penneri strain 26 was studied using sugar analysis and 1H and 13C NMR spectroscopy, including two-dimensional NMR techniques. The following structure of the trisaccharide repeating unit was established: -->6)-alpha-D-GlcpNAc-(1-->3)-alpha-L-QuipNAc-(1-->3)-alpha-D-Glcp NAc-(1--> where L-QuiNAc is 2-acetamido-2,6-dideoxy-L-glucose (N-acetyl-L-quinovosamine). Cross-reactivity of the Proteus penneri 26 anti-O serum with other strains of P. penneri isolated in Poland and USA and one strain of P. vulgaris is discussed.

Acetylglucosamine↗
PubMed1998

Structural analysis of the O-antigenic polysaccharide from Vibrio mimicus N-1990.

The O-antigenic polysaccharide part of the lipopolysaccharide from Vibrio mimicus N-1990 has been investigated. Sugar and methylation analysis of native and dephosphorylated polysaccharide together with NMR spectroscopy show that the polysaccharide is composed of tetrasaccharide repeating units. The structure of the repeating unit of the polysaccharide from V. mimicus N-1990 could be determined as: -->4)-alpha-D-GalpNAc-(1-->3)-beta-D-GalpNAc-(1-->2)-4,6-P-beta-D-Galp-( 1-->3)-alpha-D-GalpNAc-(1-->. The V. mimicus N-1990 strain cross-reacts with antibodies elicited against the Vibrio cholerae O139. The nature of this cross-reactivity resides in the partial structure comprising the galactosyl residue substituted with a cyclic phosphate. This element is present in the cell-wall-associated polysaccharides of both strains.

Carbohydrate Conformation↗