Biomedical subjects
Publications and source records attributed to A S Shashkov.
The O-specific polysaccharide of the lipopolysaccharide from H. alvei strain 38 has been established by NMR spectroscopy (13C and 1H) and methylation analysis to have the repeating unit-->4)-beta-D-ManpNAc-(1-->4)-alpha-D-GlcpNAc(1-->.
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]
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On the basis of chemical and NMR data the partial structure of lipid A from lipooligosaccharide (LOS) of Neisseria meningitidis group B, strain BC5S No 125 was established. Lipid A consisted of disaccharide 2-deoxy-6-O-[2-deoxy-2-(3-hydroxytetradecanoylamino)- beta-gluco-pyranosyl]-2-(3-hydroxytetradecanoylamino)- alpha-glucopyranose carrying the beta-(2-aminoethyl)pyrophosphate residue at 0-4' and the pyrophosphate or phosphate residue at 0-1. On hydrolysis of the acidic form of LOS with 1% acetic acid the substituent at 0-1 was practically completely removed whereas that at 0-4' was stable. The analogous hydrolysis of the Mg-salt of LOS was accompanied by splitting off the pyrophosphate linkage in the substituent at 0-4'. Hydrolysis of LOS at pH 4.5 in the presence of SDS led mainly to a lipid A preparation retaining both pyrophosphate residues.
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.
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The genetic information to synthesize the S-specific region of Shigella sonnei phase I lipopolysaccharide (LPS) is localized on a 180 kb plasmid which is lost quite readily. A recombinant plasmid derivative remaining stable in the bacteria was shown to determine the S-specific region of the LPS which is completely identical with that of a S. sonnei phase I strain following transfer in Escherichia coli K-12. However, the length control in polysaccharide biosynthesis is lost at least partially.
The O-specific moieties of the O1B antigen (lipopolysaccharide) from Escherichia coli O1B:K1 and the O1C antigen from E. coli O1C:K- both consist of L-rhamnose, D-galactose, N-acetyl-D-glucosamine, and N-acetyl-D-mannosamine in a molar ratio of 2:1:1:1. By using fragmentation procedures, methylation analysis, and one- and two-dimensional nuclear magnetic resonance spectroscopy, the structures of these polysaccharides were found to be [formula: see text] In the O1B polysaccharide X is 2, and in the O1C polysaccharide X is 3. With the recently published structure of the O1A polysaccharides (B. Jann, A. S. Shashkov, D. S. Gupta, S. M. Panasenko, and K. Jann, Carbohydr. Polym. 18:51-57 1992), three related O1 antigens are now known. Their common (O1-specific) epitope is suggested to be the side-chain N-acetyl-D-mannosamine residue.
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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.
A. beijerinckii strain B-1615 produced two acidic exopolysaccharides in the ratio approximately 9:1. The minor polysaccharide contained mannuronic and guluronic acids in the ratio 2.3:1 and is a bacterial alginate. The major polysaccharide consisted of D-galactose, L-rhamnose, and pyruvic acid in the ratios 2:1:1 and was acetylated. On the basis of methylation analysis, and 1H- and 13C-n.m.r. spectroscopy of the polysaccharide before and after removal of the pyruvic acid residues and O-deacetylation, it was concluded that the major polysaccharide had the structure [formula; see text] with up to 1.5 OAc groups per repeating unit.
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.
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.
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O-specific polysaccharide was obtained on mild acid degradation of lipopolysaccharide of Proteus vulgaris 5/43 belonging to OX19 (O-variants). It was found to contain D-glucose, 2-acetamido-2-deoxy-D-glucose, and 2-acetamido-2,6-dideoxy-L-glucose (QuiNAc, N-acetyl-L-quinovosamine) in the ratio of about 1:2:1, the last-named sugar being rather uncommon for bacterial antigens. A computer-assisted 13C-NMR-based analysis, methylation analysis, and selective cleavage with anhydrous hydrogen fluoride and dilute hydrochloric acid were applied for structural elucidation of the polysaccharide and the following structure was established:----2)-beta-D-Glcp-(1----6)-alpha-D-GlcpNAc-(1----3)- alpha-L-QuipNAc-(1----3)-beta-D-GlcpNAc-(1----. Serological studies of the O-antigen and oligosaccharides derived therefrom revealed the importance of the trisaccharide fragment beta-D-Glcp-(1----6)-alpha-D-GlcpNAc-(1----3)-alpha-L- QuipNAc in manifesting the antigenic specificity. Serological cross-reactions were demonstrated between lipopolysaccharides of P. vulgaris 5/43, 8/44, and OX19 strains.
The O-specific polysaccharide, obtained by mild acid degradation of the lipopolysaccharide of Francisella tularensis strain 15, contained 2-acetamido-2,6-dideoxy-D-glucose (D-QuiNAc), 4,6-dideoxy-4-formamido-D-glucose (D-Qui4NFm), and 2-acetamido-2-deoxy-D-galacturonamide (D-GalNAcAN) in the ratios 1:1:2. Tri- and tetra-saccharide fragments were obtained on treatment of the polysaccharide with anhydrous hydrogen fluoride and partial hydrolysis with 0.1 M hydrochloric acid, respectively. On the basis of 1H- and 13C-n.m.r. spectroscopy of the polysaccharide and the saccharides, it was concluded that the O-antigen had the structure: ----4)-alpha-D-GalpNAcAN-(1----4)-alpha-D-GalpNAcAN-(1----3) -beta-D-QuipNAc-(1----2)-beta-D-Quip4NFm-(1----. This O-antigen is related in structure to those of Pseudomonas aeruginosa O6, immunotype 1, and IID 1008, and Shigella dysenteriae type 7.