Biomedical subjects

A S Shashkov

Publications and source records attributed to A S Shashkov.

At least 37 records · Page 2Linked to original sources

PubMed2001

NMR-based identification of cell wall anionic polymers of Spirilliplanes yamanashiensis VKM Ac-1993(T).

The cell wall of Spirilliplanes yamanashiensis VKM Ac-1993(T) contains four anionic polymers, viz., three teichoic acids and a sugar-1-phosphate polymer. The following are the structures of the teichoic acids: poly[-6-beta-D-glucopyranosyl-(1-->2)-glycerol phosphate] (PI), 1,3-poly(glycerol phosphate) bearing N-acetyl-alpha-D-glucosamine residues at O-2 (70%) (PII), and poly[-6-N-acetyl-alpha-D-glucosaminyl-(1-->2)-glycerol phosphate] (PIII). The repeating unit of the fourth polymer (PIV) has the structure of -6-alpha-D-GlcpNAc-(1-->6)-alpha-D-GlcpNAc-1-P- with a 3-O-methyl-alpha-D-mannopyranosyl residues at position 3 of some 6-phosphorylated N-acetylglucosamine residues (50%). Polymers PI, PIII and PIV have not hitherto been found in prokaryotic cell walls.

Actinomycetales↗

PubMed2001

Study of glycosylation with N-trichloroacetyl-D-glucosamine derivatives in the syntheses of the spacer-armed pentasaccharides sialyl lacto-N-neotetraose and sialyl lacto-N-tetraose, their fragments, and analogues.

The syntheses of 2-aminoethyl glycosides of the pentasaccharides Neu5Ac-alpha(2-->3)-Gal-beta(1-->4)-GlcNAc-beta(1-->3)-Gal-beta(1-->4)-Glc and Neu5Ac-alpha(2-->3)-Gal-beta(1-->3)-GlcNAc-beta(1-->3)-Gal-beta(1-->4)-Glc, their asialo di-, tri-, and tetrasaccharide fragments, and analogues included a systematic study of glycosylation with variously protected mono- and disaccharide donors derived from N-trichloroacetyl-D-glucosamine of galactose, lactose, and lactosamine glycosyl acceptors bearing benzoyl protection around the OH group to be glycosylated. Despite the low reactivity of these acceptors, stereospecificity and good to excellent yields were obtained with NIS-TfOH-activated thioglycoside donors of such type, or with AgOTf-activated glycosyl bromides, while other promotors, as well as a trichloroacetimidate donor, were less effective, and a beta-acetate donor was inactive. In NIS-TfOH-promoted glycosylation with the thioglycosides, the use of TfOH in catalytic amount led to rapid formation of the corresponding oxazoline, but the quantity of TfOH necessary for further efficient coupling with an acceptor depended on the reactivity of the donor, varying from 0.07 equiv for a 3,6-di-O-benzylated monosaccharide derivative to 2.1 equiv for a peracetylated disaccharide one. In the glycosylation products, the N-trichloroacetyl group was easily converted into N-acetyl by alkaline hydrolysis followed by N-acetylation.

Acetylglucosamine↗

PubMed2001

Synthesis and NMR spectroscopy of nine stereoisomeric 5,7-diacetamido-3,5,7,9-tetradeoxynon-2-ulosonic acids.

Derivatives of 5,7-diamino-3,5,7,9-tetradeoxynon-2-ulosonic acids are essential constituents of some bacterial polysaccharides and glycoproteins. In order to establish reliably the configuration of the natural sugars, nine stereoisomeric 5,7-diacetamido-3,5,7,9-tetradeoxynon-2-ulosonic acids were synthesized, including di-N-acetyl-legionaminic and -pseudaminic acids (the D-glycero-D-galacto and L-glycero-L-manno isomers, respectively) and their isomers at C-4, C-5, C-7, and C-8 having the L-glycero-D-galacto, D-glycero-D-talo, L-glycero-D-talo, D-glycero-L-altro, L-glycero-L-altro, D-glycero-L-manno, and L-glycero-L-gluco configurations. Synthesis was performed by condensation of 2,4-diacetamido-2,4,6-trideoxy-L-gulose, -D-mannose, -D-talose, and -L-allose with oxalacetic acid under basic conditions, the reaction of the last two precursors being accompanied by epimerisation at C-2. The 1H and 13C NMR data of the synthetic compounds are discussed. Acetylated methyl esters of the C-7 and C-8 isomeric nonulosonic acids were prepared and used for analysis of the side-chain conformation by NMR spectroscopy.

Gluconates↗

PubMed2001

Computer-assisted structural analysis of regular glycopolymers on the basis of 13C NMR data.

A computer-assisted approach to the prediction of the primary structures of regular glycopolymers is described. The analysis is based on comparing the calculated 13C NMR spectra of all the possible structures of the repeating unit (for the given monomeric composition) to an experimental 13C NMR spectrum. The spectra generation is based on the spectral database containing information on the 13C chemical shifts of monomers, di- and trimeric fragments. If the required data are missing from this database, the special database for average glycosylation effects is used. The analysis reveals those structures with the calculated 13C NMR spectrum most close to observed. The structures of repeating units of any topology containing up to six residues linked by glycosidic, amidic or phospho-diester bridges can be predicted. Unambiguous selection of the proper structure from the output list of possible structures may require additional experimental data. Testing the created program and databases on bacterial polysaccharides and their derivatives containing up to three non-sugar residues (alditols, amino acids, phosphate groups etc.) per repeating unit revealed the good convergence of prediction with independently obtained structural data.

Algorithms↗

PubMed2001

Structure of the O-specific polysaccharide of Citrobacter braakii O7a,3b,1c.

The following structure of the O-specific polysaccharide of Citrobacter braakii O7a,3b,1c was established using sugar and methylation analyses and NMR spectroscopy, including 2D COSY, TOCSY, NOESY, and 1H, 13C heteronuclear single-quantum coherence (HSQC) experiments: (struture: see text). The main D-mannan chain of the polysaccharide studied has the same structure as the O-specific polysaccharide of Escherichia coli O9, Klebsiella pneumoniae O3, and Hafnia alvei PCM 1223.

Carbohydrate Sequence↗

PubMed2001

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.

Carbohydrate Sequence↗

PubMed2001

Structure of a colitose-containing O-specific polysaccharide of the marine bacterium Pseudoalteromonas tetraodonis IAM 14160(T).

O-specific polysaccharide was isolated by mild acid degradation of the lipopolysaccharide of Pseudoalteromonas tetraodonis type strain IAM 14160(T) and studied by sugar and methylation analyses along with 1H and 13C NMR spectroscopy, including 2D COSY, TOCSY, 1H,(13)C HMQC and HMBC experiments. The polysaccharide was found to consist of hexasaccharide repeating units containing one residue each of D-Gal, D-GlcA, D-GalNAc and D-GlcNAc and two residues of 3,6-dideoxy-L-xylo-hexose (colitose, Col) and having the following structure:In common with the polysaccharides of some other bacteria, the polysaccharide studied contains a tetrasaccharide fragment alpha-Colp-(1-->2)-beta-D-Galp-(1-->3)-[alpha-Colp-(1-->4)]-beta-D-GlcpNAc, which is a colitose ('3-deoxy-L-fucose') analogue of the Lewis(b) blood group antigenic determinant.

Carbohydrate Conformation↗

PubMed2001

Synthesis and identification in bacterial lipopolysaccharides of 5,7-diacetamido-3,5,7,9-tetradeoxy-D-glycero-D-galacto- and -D-glycero-D-talo-non-2-ulosonic acids.

5,7-Diacetamido-3,5,7,9-tetradeoxy-D-glycero-D-galacto- and -D-glycero-D-talo-non-2-ulosonic acids were synthesized by condensation of 2,4-diacetamido-2,4,6-trideoxy-D-mannose with oxalacetic acid. Comparison of the 1H and 13C NMR data and the specific optical rotation values of these monosaccharides and the corresponding L-glycero-D-galacto and L-glycero-D-talo isomers synthesized earlier [Tsvetkov, Y. E.; Shashkov, A. S.; Knirel, Y. A.; Backinowsky, L. V.; Zähringer, U. Mendeleev Commun. 2000, 90-92] with data of the natural compounds enabled the identification in bacterial lipopolysaccharides of derivatives of 5,7-diamino-3,5,7,9-tetradeoxy-D-glycero-D-galacto-non-2-ulosonic (legionaminic) acid and epimers of legionaminic acid at C-4 and C-8.

Legionella pneumophila↗

PubMed2001

Structure of the O-specific polysaccharide isolated from the lipopolysaccharide of Citrobacter gillenii serotype O12a, 12b strain PCM 1544.

A neutral O-specific polysaccharide was isolated from the lipopolysaccharide of Citrobacter gillenii strain PCM 1544, representing serotype O12a,12b. The polysaccharide was studied by sugar and methylation analyses and Smith degradation along with 1H and 13C NMR spectroscopy, including a ROESY experiment. The following structure of the tetrasaccharide repeating unit was established, in which substitution with terminal GlcNAc is approximately 60%. [structure: see text]

Carbohydrate Conformation↗

PubMed2001

Structure of the O-specific polysaccharide of Proteus vulgaris O4 containing a new component of bacterial polysaccharides, 4,6-dideoxy-4.

A high-molecular-mass O-specific polysaccharide was obtained by mild acid degradation of Proteus vulgaris O4 lipopolysaccharide followed by GPC. The polysaccharide was studied by chemical methods along with 1H and 13C NMR spectroscopy, including two-dimensional COSY, TOCSY, NOESY, H-detected 1H,13C HMQC, and 1H,13C HMBC experiments. Solvolysis of the polysaccharide with trifluoromethanesulfonic (triflic) acid resulted in a GlcpA-(1 --> 3)-GlcNAc disaccharide and a novel amino sugar derivative, 4,6-dideoxy-4-[N-[(R)-3-hydroxybutyryl]-L-alanyl]amino-D-glucose [Qui4N(HbAla)]. On the basis of the data obtained, the following structure of the tetrasaccharide repeating unit of the O-specific polysaccharide was established: --> 4)-beta-D-GlcpA-(1 --> 3)-beta-D-GlcpNAc-(1 --> 2)-beta-D-Quip4N(HbAla)-(1 --> 3)-alpha-D-Galp-(1 -->. This structure is unique among the O-specific polysaccharides, which is in accordance with classification of the strain studied in a separate Proteus serogroup.

Animals↗

PubMed2001

Structure of the O-specific polysaccharide of Proteus mirabilis O16 containing ethanolamine phosphate and ribitol phosphate.

The O-specific polysaccharide of Proteus mirabilis O16 was studied by 1H and 13C NMR spectroscopy, including 2D COSY, TOCSY, NOESY, H-detected 1H,13C HMQC, HMQC-TOCSY, and 1H,31P HMQC experiments, along with chemical methods. The polysaccharide was found to be a ribitol teichoic acid-like polymer having the following structure [structure: see text].

Carbohydrate Conformation↗

PubMed2001

Synthesis of Neu5Ac- and Neu5Gc-alpha-(2-->6')-lactosamine 3-aminopropyl glycosides.

In order to prepare 3-aminopropyl glycosides of Neu5Ac-alpha-(2-->6')-lactosamine trisaccharide 1, and its N-glycolyl containing analogue Neu5Gc-alpha-(2-->6')-lactosamine 2, a series of lactosamine acceptors with two, three, and four free OH groups in the galactose residue was studied in glycosylations with a conventional sialyl donor phenyl [methyl 5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-2-thio-D-glycero-alpha- and beta-D-galacto-2-nonulopyranosid]onates (3) and a new donor phenyl [methyl 4,7,8,9-tetra-O-acetyl-5-(N-tert-butoxycarbonylacetamido)-3,5-dideoxy-2-thio-D-glycero-alpha- and beta-D-galacto-2-nonulopyranosid]onates (4), respectively. The lactosamine 4',6'-diol acceptor was found to be the most efficient in glycosylation with both 3 and 4, while imide-type donor 4 gave slightly higher yields with all acceptors, and isolation of the reaction products was more convenient. In the trisaccharides, obtained by glycosylation with donor 4, the 5-(N-tert-butoxycarbonylacetamido) moiety in the neuraminic acid could be efficiently transformed into the desired N-glycolyl fragment, indicating that such protected oligosaccharide derivatives are valuable precursors of sialo-oligosaccharides containing N-modified analogues of Neu5Ac.

Carbohydrate Conformation↗

PubMed2001

Structure of the O-specific polysaccharide of Hafnia alvei PCM 1196.

An acidic O-specific polysaccharide was isolated from Hafnia alvei PCM 1196 lipopolysaccharide and studied by sugar and methylation analyses along with one- and two-dimensional 1H and 13C NMR spectroscopy, including NOESY and HMBC experiments. The following structure of the pentasaccharide repeating unit was established: -->4)-alpha-D-GalpA-(1-->3)-beta-D-GlcpNAc-(1-->2)-beta-D-Galp-(1-->6)-alpha-D-Glcp-(1-->6)-alpha-D-GlcpNAc-(1-->.

Carbohydrate Conformation↗

PubMed2001

Location of the O-methyl groups in the O polysaccharide of Pseudomonas syringae pv. phaseolicola.

The O-methylation pattern of the O polysaccharide (OPS) of the lipopolysaccharide of Pseudomonas syringae pv. phaseolicola GSPB 1552 was revealed by methylation (CD3I) analysis, Smith degradation, and NMR spectroscopy. Together with the major O repeats consisting of D-rhamnopyranose (D-Rhap) and D-fucofuranose (D-Fucf), there are minor repeats (approximately 30%) containing 3-O-methyl-D-rhamnose (D-acofriose), which is 2-substituted in the interior repeats and occupies the terminal non-reducing end of the OPS. It was suggested that the methylated O repeats are linked to each other nearby the non-reducing end of the OPS and that the 'biological' O repeat of the OPS has the following structure: [molecular structure: see text].

Carbohydrate Conformation↗

PubMed2001

Distribution of pyranose and furanose forms of 6-deoxyheptoses in water solution.

On the basis of 1H and 13C NMR spectroscopy studies, the proportion of pyranose and furanose forms of 6-deoxyheptoses in water solution was determined. Water solution of 6-deoxyheptoses contains all possible furanose and pyranose forms (except 6-deoxy-gluco-heptose for which only pyranose was found), although pyranose is dominant.

Carbohydrate Conformation↗

PubMed2001

Structure of an acidic polysaccharide from a marine bacterium Pseudoalteromonas distincta KMM 638 containing 5-acetamido-3,5,7,9-tetradeoxy-7-formamido-L-glycero-L-manno-nonulosonic acid.

An acidic polysaccharide was obtained from the lipopolysaccharide of Pseudoalteromonas distincta strain KMM 638, isolated from a marine sponge, and found to contain D-GlcA, D-GalNAc, 2-acetamido-2,6-dideoxy-D-glucose (D-QuiNAc) and two unusual acidic amino sugars: 2-acetamido-2-deoxy-D-galacturonic acid (D-GalNAcA) and 5-acetamido-3,5,7,9-tetradeoxy-7-formamido-L-glycero-L-manno-nonulosonic acid (Pse5Ac7Fo, a derivative of pseudaminic acid). Oligosaccharides were derived from the polysaccharide by partial acid hydrolysis and mild alkaline degradation and characterised by electrospray ionisation (ESI) MS and 1H and 13C NMR spectroscopy. Based on these data and NMR spectroscopic studies of the initial and O-deacetylated polysaccharides, including quaternary carbon detection, 2D COSY, TOCSY, ROESY, H-detected 1H,13C HMQC and HMBC experiments, the following structure of the branched pentasaccharide repeating unit was established: [structure: see text].

Alteromonas↗

PubMed2001

Chemical structure of the core oligosaccharide of aerotolerant Campylobacter jejuni O:2 lipopolysaccharide.

The structure of the core oligosaccharide of aerotolerant Campylobacter jejuni 0:2 lipopolysaccharide was determined and found to contain 3-deoxy-D-manno-octulosonic acid (Kdo), L-glycero-D-manno-heptose (LD-Hep), D-galactose, D-glucose, and phosphorylethanolamine (PEtn). Based on 1H, 13C and 31P NMR spectroscopic studies including 2D COSY, TOCSY, ROESY and heteronuclear 1H-31P and HMQC experiments it was established that the oligosaccharide has the following structure: [structure: see text].

Campylobacter jejuni↗

PubMed2001

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.

Antigens, Bacterial↗