Evgeny Vinogradov

Structural determination of some new oligosaccharides and analysis of the branching pattern of isomaltooligosaccharides from beer

Separation of the low molecular weight fraction of oligosaccharides from beer and subsequent NMR analysis led to the identification of several new derivatives of trehalose, sucrose, maltooligosaccharides glucosylated at O-2 of reducing end Glc, and linear Glc oligomers with alpha-(1-->3) and alpha-(1-->4)-linkages. Reducing oligosaccharides were labeled with 7-amino-4-methylcoumarin by reductive amination, separated according to their molecular weight and the branching pattern was studied using enzymatic (pullulanase) degradation in combination with MALDI-TOF mass spectrometry and HPLC analysis. It was found that up to DP 10 isomaltooligosaccharides mostly consisted of a linear reducing alpha-(1-->4)-linked Glc chain substituted by single maltose or maltotriose residue at O-6 of any residue except the reducing one.

A New Type of Glycosidic Linkage: An Open-Chain Acetal-LinkedN-Acetylgalactosamine in the Core Part of the Lipopolysaccharides fromProteus Microorganisms

Chemical stability similar to that of a normal glycosidic linkage is displayed by the novel acetal linkage between monosaccharides through the structural element shown. This survives hydrolysis with dilute acetic acid, but is cleaved under the hydrolytic conditions normally used in monosaccharide analysis (2 M HCl)-a possible reason why the structural element has only now been identified.

Characterization of a Novel Branched Tetrasaccharide of 3-Deoxy-d-manno-oct-2-ulopyranosonic Acid THE STRUCTURE OF THE CARBOHYDRATE BACKBONE OF THE LIPOPOLYSACCHARIDE FROM ACINETOBACTER BAUMANNII STRAIN NCTC 10303 (ATCC 17904)

 For the first time, the tetrasaccharide Kdoα2→5Kdoα2→5(Kdoα2→4)Kdo (Kdo is 3-deoxy-d-manno-oct-2-ulopyranosonic acid) has been identified in a bacterial lipopolysaccharide (LPS),i.e. in the core region of LPS from Acinetobacter baumannii NCTC 10303. The LPS was analyzed using compositional analysis, mass spectrometry, and NMR spectroscopy. The disaccharided-GlcpNβ1→6d-GlcpN, phosphorylated at O-1 and O-4′, was identified as the carbohydrate backbone of the lipid A. The Kdo tetrasaccharide is attached to O-6′ of this disaccharide and is further substituted by shortl-rhamnoglycans of varying length and by the disaccharided-GlcpNAcα1→4d-GlcpNA (GlcpNA, 2-amino-2-deoxy-glucopyranosuronic acid). The core region is not substituted by phosphate residues and represents a novel core type of bacterial LPS. The complete carbohydrate backbone of the LPS is shown in Structure I as follows: Kdo α 2 → 4 Kd 5 ↑ Glc p NAc α 1 → 4 Glc p NA α 1 → 4 Kdo α 2 5       ↑       L Rha p ∗ α 1 → 3 L Rha p ∗ α 1 → 3 L Rha p α 1 → 3 L Rha p α 1 → 8 Kdo α 2       o α 2 → 6 Glc p N β 1 → 6 Glc 4   ↑   P   p N α 1 → P STRUCTURE I where Rha is rhamnose. Except were indicated, monosaccharides possess thed-configuration. Sugars marked with an asterisk are present in non-stoichiometric amounts.

The structure of the core part of Proteus vulgaris OX2 lipopolysaccharide

The identity of a novel structural component, an open-chain acetalic linkage, in the core part of the lipopolysaccharide (LPS) from Proteus vulgaris serotype OX2 has been determined by extensive NMR spectroscopic analysis of fragments isolated after mild acid hydrolysis of the intact LPS. The open-chain N-acetylgalactosamine fragment is substituted in the 4-position by non-stoichiometric amounts of a beta-galactopyranose residue and the overall structure of the core is as follows: [formula: see text] All sugars except the N-acetylgalactosamine are in the pyranose form, alpha-Hep refers to L-glycero-alpha-D-manno-heptopyranose and alpha-DDHep to D-glycero-alpha-D-manno-heptopyranose. Bold italics indicate non-stoichiometric substituents.

Isolation and characterization of non-labeled and 13C-labeled mannans from Pichia pastoris yeast

Mannans from genetically modified Pichia pastoris yeast, used for overproduction of neural cell adhesion molecule protein, grown on normal media or on uniformly 13C-labeled glucose and methanol, were isolated and characterized by high-field (750 MHz) NMR spectroscopy. Fully 13C-labeled oligosaccharide fragments were prepared from mannans by acetolysis. According to the data obtained, the mannan is made up of a main chain of alpha-(1-->6)-linked mannopyranosyl residues, substituted at 0-2 with alpha-mannopyranosyl or a alpha-D-Manp-(1-->2)-beta-D-Manp-(1-->2)-beta-D-Manp-( 1-->2)-alpha-D-Manp- group, and with much lower content of substitution with beta-D-Manp-(1-->2)-alpha-D-Manp-. A fraction of these oligosaccharide side chains is again substituted with alpha-D-Glcp or alpha-D-GlcpNAc through a phosphodiester linkage to the 6 position of the first mannopyranosyl residue. Improved conditions of acetolysis, cleaving all alpha-(1-->6) linkages, but not beta-mannoside linkages, are proposed.

The structure of the core part of Proteuspenneri strain 16 lipopolysaccharide

The structure of the carbohydrate backbone of the lipid A-core region of the lipopolysaccharide (LPS) from Proteus penneri strain 16 was determined using NMR and chemical analysis of the core oligosaccharide, obtained by mild acid hydrolysis of the LPS, and of the products of alkaline deacylation of the LPS: formula [see text]. Incomplete substitution is indicated by bold italics. All sugars are in the pyranose form, alpha-Hep is the residue of L-glycero-alpha-D-manno-Hep, alpha-DD-Hep is the residue of D-glycero-alpha-D-manno-Hep, Bu is the (R)-3-hydroxybutyryl residue.

Eine glycosidische Bindung neuen Typs: ein offenkettigesN-Acetylgalactosaminacetal, gebunden im Kernbereich der Lipopolysaccharide vonProteus-Mikroorganismen

Ahnlich stabil wie die normale glycosidische Bindung ist die neuartige Verknupfung von Monosacchariden uber das abgebildete Strukturelement. Dieses ubersteht die Hydrolyse mit verdunnter Essigsaure, wird aber durch die ubliche Hydrolyse mit 2 M HCl gespalten – ein moglicher Grund dafur, das das Strukturelement erst jetzt identifiziert wurde.