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Biomedical subjects

L Kenne

Publications and source records attributed to L Kenne.

101 records · Page 6Linked to original sources
PubMed1978

Structural studies of Shigella flexneri O-antigens.

The structures of the O-antigens of all known serotypes and subserotypes of Shigella flexneri have been reinvestigated. The results support the assumption that these antigens are composed of a basic tetrasaccharide repeating unit (1), to which alpha-D-glucopyranosyl and/or O-acetyl groups are attached at different positions. Leads to 3)-beta-D-GlcNAcp-(1 leads to 2)-alpha-L-Rhap-(1 leads to 2)-alpha-L-Rhap-(1 leads to 3)-alpha-L-Rhap-(1 leads to The immunological determinants responsible for O-factors I, II, IV, V and 7, 8 contain alpha-D-gluco-pyranosyl groups, the locations of which have been determined. O-Factor 6 is due to O-acetyl groups, linked to O-2 of the 3-substituted alpha-L-rhamnopyranosyl residue in unit 1 and O-factor III seems to be due to the same groups. The chemical natures of the determinants responsible for O-factors 4 and 3, 4 are still obscure. The structural studies indicate that the immunological classification of Sh. flexneri serotypes and subserotypes, as regards these O-factors, may need revision.

Carbohydrates↗
PubMed1977

Structural studies of the Shigella flexneri variant X, type 5 a and type 5 b O-antigens.

Previous studies of different Shigella flexneri O-antigens indicate that their O-specific region is composed of oligosaccharide repeating units containing a basic tetrasaccharide structure, to which alpha-D-glucopyranosyl groups and O-acetyl groups may be attached to different positions. Structural studies of O-antigens from variant X, type 5a and type 5b lend further support to this assumption. These antigens contain terminal alpha-D-glucopyranosyl groups, one each per repeating unit in X and 5a, two in 5b. The location of these groups in the repeating unit has been determined.

Carbohydrates↗
PubMed1975

The structure of capsular polysaccharide of the Pneumococcus type II.

The pneumococcus type II capsular polysaccharide (SII) is composed of singly-branched hexasaccharide repeating units, for which three alternative structures have been proposed. The correct structure has now been determined by consecutive eliminations of the sugar residues in the side chain. The terminal D-glucuronic acid group was eliminated by treating the fully methylated and esterified SIIpolysaccharide first with base, and then with weak acid. The hydroxyl group at C-6 in the penultimate D-glucose residue released by this elimination was transformed into the 6-deoxy-6-tosyl derivative, and the residue thereafter eliminated by treatment with base. As the side-chains were eliminated by these reactions, it is considered that they contain only two sugar residues, which thus excludes two of the three alternative structures. Structure 1 was further confirmed by subjecting SII to a Smith degradation, which yielded the tetrasaccharide L-Rhap-(1 yields 3)-L-Rhap-(1 yields 3)-L-Rhap-(1 yields 2-erythritol, characterised by methylation analysis.

Chromatography, Gas↗
PubMedDate not supplied

On the chemistry of the reaction between N-acetylcysteine and 4-[(4-ethoxyphenyl)imino]-2,5-cyclohexadien-1-one, a 4-ethoxyaniline metabolite formed during peroxidase reactions.

4-Ethoxyaniline (p-phenetidine) is oxidized by peroxidases to form several products, one of which is 4-[(4-ethoxyphenyl)imino]-2,5-cyclohexadien-1-one (1). This compound reacts with N-acetylcysteine (NAC) in methanol-phosphate buffers, generating at least four different products. Four major products, 4-[(4-ethoxyphenyl)amino]phenol (2), 3-(N-acetylcystein-S-yl)-4-[(4-ethoxyphenyl)amino]phenol (3), 2,5-bis(N-acetylcystein-S-yl)-4-[(4-ethoxyphenyl)-amino]phenol (4), and 2,5-bis(N-acetylcystein-S-yl)-4-[(4-ethoxyphenyl)imino]-2,5- cyclohexadien-1-one (5), were isolated and identified by NMR spectroscopy and mass spectrometry. The relative ratio between the formed products depends on the pH, the concentration of NAC, and the reaction time. Compound 2, which is the reduced form of 1, was the dominating product when the reaction took place at pH 3, whereas formation of the mono conjugate (3) was more extensive at a neutral pH. Under alkaline conditions 2 and 3 were oxidized by 1 or O2. The oxidized form of 3 was subsequently attacked by a second molecule of NAC, generating the bis conjugate (4). Unless an excess of NAC was present, compound 4 underwent rapid oxidation to 5. Quinone imines, like 1, generating mono conjugates, which are more reactive than the quinone imines per se, are likely to inflict an increased toxic potential and an increased stress on the endogenous thiol pool, resulting in an overall greater toxicity.

Acetylcysteine↗