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N K Kochetkov

Publications and source records attributed to N K Kochetkov.

At least 19 recordsLinked to original sources
PubMed1992

Computer-assisted analysis of the structure of regular branched polysaccharides containing 2,3-disubstituted rhamnopyranose and mannopyranose residues on the basis of 13C NMR data.

A computer-assisted approach to the analysis of the structure of branched polysaccharides that contain 2,3-di-O-glycosylated alpha-rhamnopyranose and alpha-mannopyranose residues is based on evaluation of the 13C NMR spectra, using glycosylation effects and their deviations from additivity (delta delta values) at the branch points. This approach, in combination with monosaccharide and methylation analysis data, has been verified on a series of bacterial polysaccharides of known structure.

Carbohydrate Sequence↗
PubMed1992

Synthesis of a heteroglycuronan derivative containing the beta-D-galactopyranosyluronic acid (1-->3)-L-rhamnose repeating unit.

Helferich glycosylation of the cyanoethylidene L-rhamnose derivative 3 with the galactosyluronic bromide 2 gave the disaccharide 4 as a key intermediate in the synthesis of the monomer 13 for trityl-cyanoethylidene condensation (TCC). The following formation of the monomer 13, including introduction of a trityl group at O-3', proceeded in six steps. Because of the difficulty of some steps, an alternative route for 13 was tested. Model compounds 20, 21, and 22 were synthesized in order to confirm the stereoregularity of the products of the polycondensation. The polycondensation of the monomer gave D-GalpA-(1-->3)-L-Rha-oligomer derivatives consisting mainly of three repeating units. This result is in contrast with the degree of polymerisation (dp > or = 22) of other synthetic rhamnans, but is very similar to dp 2-7 of homo- and hetero-glucuronan derivatives.

Carbohydrate Sequence↗
PubMed1992

Structure of the polysaccharide chains of Pseudomonas pseudomallei lipopolysaccharides.

The pathogenic bacterium Pseudomonas pseudomallei strain 57576 produces two partially O-acetylated O-antigenic polysaccharides (PS-I and PS-II). Methylation analysis and 1H and 13C NMR spectroscopy, including NOE experiments, showed PS-I to have the structure [formula: see text] and PS-II to have the structure [formula: see text] where 6dmanHep is the unusual higher sugar 6-deoxy-D-manno-heptose. PS-II is produced also by P. pseudomallei strains 100 and 110, and PS-I and O-deacetylated PS-II by strain 97.

Burkholderia pseudomallei↗
PubMed1992

The structure of the O-specific polysaccharide chain of the lipopolysaccharide of Salmonella arizonae O61.

The O-specific polysaccharide was obtained by mild degradation of the Salmonella arizonae O61 lipopolysaccharide with acid. It contained 2-acetamido-2-deoxy-D-glucose, 2-acetamidino-2,6-dideoxy-L-galactose (FucAm), and 7-acetamido-3,5,7,9-tetradeoxy-5-[(R)-3-hydroxybutyramido]-D- glycero-L-galacto-nonulosonic acid (Sug). On the basis of partial acid hydrolysis with 0.1 M HCl, solvolysis with anhydrous HF in methanol, and 1H- and 13C-NMR analysis (including 1H/13C inversely correlated spectroscopy for localisation of N-acyl substituents), it was concluded that the O-specific polysaccharide had the following structure. ----3)-alpha-L-FucAm-(1----3)-alpha-D-GlcNAc-(1----8)-beta-Sug+ ++-(2---- The O-antigen of S. arizonae O61 is structurally related to that of Pseudomonas aeruginosa O12, thus explaining the known serological cross-reactivity between these micro-organisms.

Carbohydrate Conformation↗
PubMed1992

The structure of a glycerol teichoic acid-like O-specific polysaccharide of Hafnia alvei 1205.

The O-specific polysaccharide of Hafnia alvei 1205 contained D-glucose, D-galactose, 2-acetamido-2-deoxy-D-glucose, 4-acetamido-4,6-dideoxy-D-glucose (Qui4NAc), glycerol, phosphate, and O-acetyl groups. On the basis of 1D and 2D shift-correlated homonuclear and 13C-1H heteronuclear NMR spectroscopy, methylation analysis, Smith degradation, and dephosphorylation with hydrofluoric acid, it was concluded that the O-antigen was a partially O-acetylated teichoic acid-like polysaccharide having the following structure: [formula: see text]

Carbohydrate Conformation↗
PubMed1992

Synthesis of lysine-containing fragments of the Proteus mirabilis O27 O-specific polysaccharide and neoglycoconjugates therefrom.

Amide-linked lysine mono- and di-uronic acid fragments of the O-specific polysaccharide from P. mirabilis O27 have been synthesised. N epsilon-Boc-L-lysine tert-butyl ester was condensed with 2-azidoethyl glycosides of glucuronic acid and beta-D-GlcpNAc-(1----3)-beta-D-GlcpA. Transformation of the products into 2-acrylamidoethyl glycosides, followed by deprotection using trifluoroacetic acid, gave the target monomers that were converted into high-molecular-weight copolymer-type neoglycoconjugates.

Carbohydrate Sequence↗
PubMed1992

Synthesis of di-O-glycosyl derivatives of methyl alpha-L-rhamnopyranoside.

The syntheses are described of 2,3-di-O-glycosyl derivatives (1-12) of methyl alpha-L-rhamnopyranoside where the glycosyl moieties are variously alpha-L-fucopyranose, beta-L-fucopyranose, beta-D-glucopyranose, alpha-D-mannopyranose, and alpha-L-rhamnopyranose. The syntheses involve stereoselective glycosylation of methyl 4-O-benzoyl-3-O-(2,3,4-tri-O-benzoyl-alpha-L- rhamnopyranosyl)-alpha-L-rhamnopyranoside (21), methyl 4-O-benzoyl-3-O-(2,3,4,6-tetra-O-benzoyl-alpha-D-mannopyranosyl)- alpha-L-rhamnopyranoside (25), methyl 4-O-benzoyl-3-O-(2,3,4,6-tetra-O-benzoyl-beta-D-glucopyranosyl)- alpha-L-rhamnopyranoside (29), methyl 4-O-benzoyl-3-O-(2,3,4-tri-O-benzoyl-beta-L-fucopyranosyl)-alpha-L- rhamnopyranoside (35), and methyl 4-O-benzyl-2-O-(2,3,4-tri-O-benzoyl-beta-L-fucopyranosyl)- alpha-L-rhamnopyranoside (59). In the syntheses of compounds 7-9, the alpha-L-fucopyranosyl residues are introduced stereoselectively, using 2,3,4-tri-O-benzoyl-alpha-L-fucopyranosyl bromide (17) and ethyl 2,3,4-tri-O-acetyl-1-thio-beta-L-fucopyranoside (47) as glycosyl donors.

Carbohydrate Conformation↗
PubMed1992

[Mono- and polyspecific glycoconjugates based on synthetic O-antigen determinants of Salmonella and their serological characteristics].

Mono- and polydeterminant synthetic antigens have been prepared via copolymerisation of acrylamide with allyl-, 2-acrylamidoethyl, and p-acrylamidophenyl glycosides of di- and trisaccharides representative of the group-specific Salmonella O-antigenic determinants (0:2, 0:3, 0:4, and 0:9). Serological specificity of the glycoconjugates obtained has been studied in enzyme immunoassay (EIA) using monoreceptor antisera.

Carbohydrate Sequence↗
PubMed1992

[SCAN program for structural analysis of linear polysaccharides based on 13C-NMR spectral data using personal computers].

A programme SCAN was elaborated for the 13C NMR--based structural analysis of regular polysaccharides, which represents our earlier programme (Lipkind G.M. et al. Carbohydr. Res. 1988. V. 175. No 1. P. 59-75) modified for IBM-PC-compatible personal computers. SCAN was successfully applied for the structural elucidation of 24 polysaccharides of bacterial origin. Optimal combinations of the computer-assisted method with other approaches for analysis of carbohydrates and scopes of application of the programme are discussed.

Carbohydrate Conformation↗
PubMed1991

N.m.r. and conformational analysis of some 2,3-disubstituted methyl alpha-L-rhamnopyranosides.

Conformational studies of the branched trisaccharide glycosides X-(1----2)[Y-(1----3)]-alpha-L-Rha-OMe (where X and Y are residues of alpha-L-, beta-L-, alpha-D-, and beta-D-hexopyranoses) were based on 1H- and 13C-n.m.r. data (n.O.e.'s, 13C chemical shifts) and theoretical calculations. In the majority of the trisaccharide glycosides, there is insignificant restriction of rotation around the glycosidic linkages in the disaccharide units as compared to the corresponding disaccharide glycosides X-(1----2)-alpha-L-Rha-OMe and Y-(1----3)-alpha-L-Rha-OMe. Differences in the conformations observed for several compounds resulted in changes of the n.O.e. patterns and in deviations from additivity of glycosylation effects in the 13C-n.m.r. spectra.

Carbohydrate Conformation↗
PubMed1991

Structure of the capsular polysaccharide and the O-side-chain of the lipopolysaccharide from Acetobacter methanolicus MB 58/4 (IMET 10945), and of oligosaccharides resulting from their degradation by the bacteriophage Acml.

The capsular polysaccharide (CPS) and the O-side-chain of the lipopolysaccharide (LPS) of Acetobacter methanolicus MB 58/4 (IMET 10945) have been shown to contain the same disaccharide repeating unit, namely, ----2)-beta-D-Galf-(1----3)-beta-D-Galp-(1----. Degradation of the CPS and the LPS with the bacteriophage Acml gave fragments built up of 1-5 repeating units; the octasaccharide preponderated. The phage-associated depolymerase proved to be a beta-D-galactofuranoside hydrolase.

Acetobacter↗
PubMed1991

Synthesis of carbohydrate-amino acid conjugates related to the capsular antigen K54 from Escherichia coli O6:K54:H10 and artificial antigens therefrom.

The disaccharides alpha-L-Rhap-(1----3)-beta-D-GlcpA and beta-D-GlcpA-(1----3)-alpha-L-Rhap bearing amide-linked L-serine or L-threonine, which represent the repeating unit(s) of the capsular polysaccharide from E. coli O6:K54:H10, have been synthesised. O-tert-Butyl-protected amino acid tert-butyl esters were condensed with the corresponding biouronic acid as the 2-acrylamidoethyl or 2-azidoethyl glycosides. The azido function was replaced by the acrylamido group by catalytic hydrogenation followed by N-acryloylation. The tert-butyl groups were removed by treatment with trifluoroacetic acid to give the target monomers which were copolymerised with acrylamide to give neoglycoconjugates that are potentially useful for immunochemical studies.

Antigens, Bacterial↗