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G Kogan

Publications and source records attributed to G Kogan.

30 records · Page 2Linked to original sources
PubMed1995

Structural elucidation of the novel type VII group B Streptococcus capsular polysaccharide by high resolution NMR spectroscopy.

The type VII capsular polysaccharide isolated from the newly discovered group B Streptococcus (GBS) strain contains D-glucose, D-galactose, N-acetyl-D-glucosamine and N-acetylneuraminic acid in the molar ratio 2:2:1:1. High-resolution one- and two-dimensional (1D and 2D) 1H and 13C NMR spectroscopy of the native and desialylated polysaccharides showed the type VII GBS capsular polysaccharide to contain the following branched hexasaccharide repeating unit: [formula: see text] Despite extensive structural similarity with the previously described GBS polysaccharides, the type VII polysaccharide showed no cross-reaction with the heterologous antisera.

Acetylglucosamine↗
PubMed1993

Structural analysis of O4-reactive polysaccharides from recombinant Escherichia coli. Changes in the O-specific polysaccharide induced by cloning of the rfb genes.

In previous studies it had been shown that lipopolysaccharide from O4-specific recombinant Escherichia coli, had serological reactivities and a chemical composition that differed from wildtype O4 LPS [Haraguchi, G.E., Zähringer, U., Jann, B., Jann, K., Hull, R.A. & Hull, S.I. (1991) Microb. Pathog. 10, 351-361]. Here we present the structural elucidation of the O-specific moieties from lipopolysaccharides of some of the recombinant strains obtained in previous studies. Compositional analysis, methylation, chemical reactions and NMR spectroscopy showed that, during genetic manipulations (recombination, cosmid cloning, plasmid subcloning), a gradual structural change in the O-specific polysaccharides was observed in the recombinant strains. These changes comprised of an alteration in the position of glucose (side chain) substitution, a change in the anomeric configuration of the main-chain N-acetylglucosamine and an exchange of alpha-L-rhamnopyranose for beta-D-galactofuranose. The relevance of these results for lipopolysaccharide cloning and lipopolysaccharide biosynthesis are discussed.

Carbohydrate Sequence↗
PubMed1993

Structure of the O56 antigen of Escherichia coli, a polysaccharide containing 7-substituted alpha-N-acetylneuraminic acid.

The O56 polysaccharide moiety of the O56 antigen (LPS) consists of D-glucose, D-galactose, 2-acetamido-2-deoxy-D-glucose, and N-acetylneuraminic acid in the molar ratios 1:1:1:1. Methylation analysis, periodate oxidation, mild acid hydrolysis, as well as 1H and 13C NMR spectroscopy showed that the O56 polysaccharide has the primary structure [formula: see text]

Carbohydrate Conformation↗
PubMed1993

Glucomannan from Candida utilis. Structural investigation.

Structure of the glucomannan isolated from the cell walls of Candida utilis has been investigated using acetolysis fragmentation, methylation analysis and NMR spectroscopy. The structure of the glucomannan resembles that of the cellular mannans of other Candida species, except that the longer tetra- and pentassacharide side-chains are terminated with a glucosyl residue. Presence of the nonreducing glucosyl groups at the ends of the side-chains caused the C. utilis not to cross-react in a double immunodiffusion test with other Candida species that possess mannan antigens and cross-react with Hansenula species with glucomannan antigens.

Candida↗
PubMed1992

Structure of the Escherichia coli 0104 polysaccharide and its identity with the capsular K9 polysaccharide.

The 0104 antigen (lipopolysaccharide, LPS) of Escherichia coli has an acidic O specific polysaccharide. From the aqueous phase of a phenol water extraction of E. coli O104: K-, a fraction was obtained by ultracentrifugation and Cetavlon precipitation of the supernatant, which was enriched in long-chain LPS. Compositional analysis, NMR spectroscopy, periodate oxidation and methylation analysis showed that the polysaccharide chain of O104 LPS II consisted of galactose, N-acetylgalactosamine and neuraminic acid and acetate in the molar ratio of 2:1:1:1 and contained 3-beta Gal, 3-beta GalNAc, 4-alpha Gal, and 4-alpha(9-OAc-NeuNAc) in linear sequence. The same results were obtained with the capsular K9 polysaccharide from E. coli O9:K9, as presented here and reported previously (Dutton et al. (1987) Carbohydr. Res. 170, 193-206).

Bacterial Capsules↗
PubMed1990

Immunochemical and structural analysis of the cell wall mannan as the basis of the taxonomic reidentification of a yeast strain.

The immunochemical properties and structural features of D-mannans from two Candida parapsilosis strains were studied. Weak cross-reactivity of D-mannans with antisera produced to C. parapsilosis strains was observed, as well as significant differences in the mannans structures were found by means of methylation analysis, acetolysis and 1H-NMR spectroscopy. In view of the discrepancies found, new taxonomic identification of one strain was carried out. On the basis of assimilation of potassium nitrate and formation of hat-shaped spores as well as other differences found by investigation of physiological characteristics, one strain of C. parapsilosis was reidentified as Hansenula anomala. This work demonstrates that immunochemical and structural investigations of cell-wall polysaccharide components can serve as a basis for taxonomic identification of yeast strains.

Candida↗
PubMed1988

Novel structure of the cellular mannan of the pathogenic yeast Candida krusei.

On the basis of methylation analysis, 13C- and 1H-n.m.r. spectroscopic data, and the results of immunological methods, a new structure for the cell-wall alpha-D-mannan of the pathogenic yeast Candida krusei is proposed. In contrast to the alpha-D-mannans of other pathogenic yeasts of the Candida species, which have (1----6)-linked main chains and many (1----2)- and/or (1----3)-linked side chains, the C. krusei mannan is lightly branched and contains (1----2) and (1----6) linkages in the ratio 3:1.

Acetylation↗
PubMed1988

Structural studies of mannans from the cell walls of the pathogenic yeasts Candida albicans serotypes A and B and Candida parapsilosis.

A comparative study of three cell-wall mannans, of Candida albicans serotypes A and B and Candida parapsilosis, by means of methylation analysis supports a model of yeast mannans as having an alpha-(1----6)-linked backbone with some units (depending on the origin of the mannan) being substituted at O-2 with oligosaccharides joined by alpha-(1---2) and, to a lesser extent, by alpha-(1----3) glycosidic bonds. Branching points in the side chains of Candida albicans mannans were found in substantial proportions for the first time, and the corresponding branched hexasaccharides were isolated by means of acetolysis and subsequent gel filtration. 13C-N.m.r. spectroscopy of the mannans, as well as a 1H-n.m.r. spectroscopic study of the oligosaccharides obtained on acetolysis of the mannans, led to results that agreed with those of methylation analysis.

Candida↗
PubMedDate not supplied

Systemic venous enhancement patterns during dynamic abdominal CT.

In 25 patients we assessed the enhancement of abdominal venous structures during dynamic computed tomography (CT). The degree of venous enhancement demonstrated great variation. In six instances (out of 250 observations) a vessel was visually perceived as not enhancing and potentially thrombosed, including three gonadal veins. CT measurements were helpful in identifying enhancement, but were occasionally low enough that thrombosis remained a radiological consideration. The great variation in venous enhancement makes the diagnosis of thrombosis suspect, based on CT alone. Corroboration of this finding is suggested, when clinically relevant.

Abdomen↗
PubMedDate not supplied

[Structure and various characteristics of yeast beta-D-glucans].

Yeast cell wall contains mainly polysaccharides. Among them beta-1,3-D-glucans play role of the skeletal carcass of the yeast cell wall, while D-mannans represent its surface antigens. Mannans are built of alpha-1,6-linked polymannosyl backbone with the side chains consisting of alpha-1,2- and alpha-1,3-linked mannosyl units. The branching degree and length of the side chains are specific for individual yeast strains. By means of subsequent alkaline and acid extractions mannans and soluble glucans can be separated, leaving insoluble particulate glucan. The latter is inhomogenous and consists of microfibrillar and amorphous components. By means of gamma-irradiation these two components were separated and the structure of each was determined. It was found that microfibrillar glucan had a structure close to that of immunomodulating glucans isolated from Japanese fungi. By means of carboxymethylation of particulate glucan its water-soluble derivatives were prepared. Some immunopharmacological properties of the particulate glucan and its soluble derivatives are discussed in relation to their structural and physico-chemical characteristics.

Chromatography, Gel↗