Haralambos Parolis

The structure of the exopolysaccharide produced by the halophilic Archaeon Haloferax mediterranei strain R4 (ATCC 33500).

The halophilic Archaeon Haloferax mediterranei exudes into the growth medium a high molecular weight sulfated polysaccharide. The structure of the repeating unit of this polymer was determined by a combination of glycose, methylation, and sulfate analysis, periodate oxidation, and 1D and 2D NMR spectroscopic analysis of the native and periodate-oxidised/reduced polysaccharides. The location of the sulfate group was established from the 1H and 13C NMR data. The structure of the repeating unit of the polysaccharide may be written as [formula: see text]

The mucilage of Opuntia ficus-indica☆

Abstract The mucilage extracted from the cladodes (modified stems) of Opuntia ficus-indica contains residues of d -galactose, d -xylose, l -arabinose, l -rhamnose, and d -galacturonic acid. Seasonal variation in the sugar composition of the mucilage has been investigated. Fractionation studies indicate that the mucilage is essentially homogeneous. The rate of release of the constituent sugars and the change in optical rotation on mild hydrolysis coupled with the results of chromic acid oxidation suggest that the mucilage contains α-arabinofuranosyl, β-xylopyranosyl, β-rhamnopyranosyl, β-galactopyranosyl, and α-galactopyranosyluronic acid residues. The results also suggest a core containing galacturonic acid, rhamnose, and galactose, to which xylose and arabinose are attached in peripheral positions.

Methylation analysis of the mucilage of Opuntia ficus-indica☆

Abstract The mucilage of Opuntia ficus-indica and a partially degraded mucilage have been investigated by methylation analysis and periodate oxidation. The results show that the mucilage is composed of 1,4-α- D -galactopyranosyluronic acid and 1,2-β- L - rhamnopyranosyl residues to which are attached short chains of 1,6-β- D -galacto-pyranosyl residues at position 4 of all of the rhamnopyranosyl residues. Most of the galactosyl residues in the side chains carry branches at O–3, while some are also branched at O–4. The branches are mainly composed of 1,5-linked arabinofuranosyl, end-group arabinofuranosyl, and end-group xylopyranosyl residues.

The extracellular polysaccharide of Pichia (Hansenula) holstii NRRL Y-2448: the phosphorylated side chains

The exopolysaccharide produced by Pichia (Hansenula) holstii NRRL Y-2448 is composed of a phosphomannan core to which oligosaccharide diester phosphate side chains are appended. The oligosaccharides of the side chains were released as oligosaccharide phosphates and neutral oligosaccharides by mild hydrolysis with aqueous acetic acid and aqueous hydrogen fluoride, respectively. The liberated oligosaccharide phosphates were studied by NMR spectroscopy and by electrospray and fast atom bombardment mass spectrometry. The structures of the neutral oligosaccharides were determined by 1D and 2D NMR spectroscopic experiments. Further insight into the length of the side chains was obtained from a matrix assisted laser desorption ionisation-time of flight mass spectrometric study of high and low molecular weight fragments obtained from partial acid hydrolysis of the native polysaccharide.

The structure of the exocellular polysaccharide produced by the Archaeon Haloferax gibbonsii (ATCC 33959)

The structure of the neutral exocellular polysaccharide isolated from the Archaeon Haloferax gibbonsii (ATCC 33959) has been determined using acid hydrolysis, methylation analysis and NMR spectroscopy. The polysaccharide contained D-Man, D-Glc, D-Gal and L-Rha in the ratios 2:1:3:1. The substitution patterns of the sugar residues were deduced from the methylation analysis which indicated the polymer to be composed of a heptasaccharide repeating unit containing two branches. The 1H and 13C NMR resonances of the component sugars were assigned using COSY, HOHAHA, HMQC, and HMQC-TOCSY 2D NMR experiments and the sequence of the sugars in the repeating unit was determined from NOESY and HMBC experiments. The structure can be written as: [formula: see text]

Structural studies on the Shigella-like Escherichia coli O121 O-specific polysaccharide

The O-specific polysaccharide isolated from the lipopolysaccharide (LPS) of Escherichia coli O121 by mild acid hydrolysis has been studied using mainly NMR spectroscopy. The polysaccharide was treated with mild base to yield a O-deacetylated polysaccharide which contained D-GlcNAc, D-GalNAcA, D-GalNAcAN (2-acetamido-2-deoxy-D-galacturonamide) and D-Qui4NAcGly (where D-Qui4N is 4-amino-4,6-dideoxy-D-glucose) in equimolar proportions. The presence of the amide was confirmed by recording the 1H NMR spectrum of the O-deacetylated polysaccharide at different pH values. The O-acetyl group was located on O-3 of the GalNAcAN and the structure of the polysaccharide can be written as [sequence: see text] This structure is almost identical to that previously reported for the O-specific polysaccharide of Shigella dysenteriae type 7 LPS, the only difference being that O-acetylation is stoichiometric in the latter.

The acid-labile, peripheral chains of the mucilage of Opuntia ficus-indica

Abstract Partial hydrolysis of the mucilage of O. ficus-indica affords O-β- d -galactopyranosyl-(1→6)- d -galactose, the polymer-homologous trisaccharide, and fourteen oligosaccharides that contain arabinose and most of which have xylosyl end-groups. O-β- d -Xylopyranosyl-(1→5)- l -arabinofuranose and O-β- d -xylopyranosyl-(1→5)-O-α- l -arabinofuranosyl-(1→5)- l -arabinofuranose were the oligosaccharides isolated in greatest amount. The most-important structural features found in the peripheral chains in the mucilage are discussed.

Sulphated polysaccharides of the Solieriaceae family : Part I. A polysaccharide from Anatheca dentata

Abstract Hot-water extraction of Anatheca dentata , a red seaweed belonging to the family Solieriaceae , yielded a mixture of polysaccharides. Fractionation of this mixture with Cetavlon gave a glucomannan as minor component and a highly sulphated, major component, which yielded D - and L -galactose, D -xylose, and traces of 3- O -methylgalactose and uronic acid on hydrolysis. Partial hydrolysis of the major component with acid gave 4- O -β- D -galactopyranosyl- L -galactose ( 1 ), 3- O -α- L -galactopyranosyl- D -galactose ( 2 ), 4- O -β- D -galactopyranosyl- D -galactose ( 3 ), O -β- D -galactopyranosyl-(1→4)- O -α- L -galactopyranosyl-(1→3)- D -galactose ( 4 ), and O -β- D -galactopyranosyl-(1→4)- O -α- L -galactopyranosyl-(1→3)- O - D -galactopyranosyl-(1→4)- L -galactose ( 5 ). The results indicate that a substantial part of the molecule has alternating D - and L -galactose residues and α-(1→3)- and β-(1→4)-glycosidic links. However, no role for the excess of D - over L -galactose, or of the xylose, has yet been found.

Sulphated polysaccharides of the grateloupiaceae family : Part VI. A polysaccharides from pachymenia carnosa

Abstract Pachymenia carnosa , a red seaweed of the Grateloupiaceae , yielded a sulphated polysaccharide which, on acid hydrolysis, gave D -galactose, 2- O -methyl- D -galactose, 4- O -methylgalactose, and 6- O -methyl- D -galactose. Partial hydrolysis of the polysaccharide resulted in the isolation and characterisation of 4- O -β- D -galactopyranosyl- D -galactose, 4- O -β- D -galactopyranosyl-2- O -methyl- D -galactose, 3- O -(2- O -methyl- D -galactopyranosyl)- D -galactose, 4- O -(6- O -methyl-β- D -galactopyranosyl)- D -galactose, 2- O -methyl-4- O -(6- O -methyl-β- D -galactopyranosyl)- D -galactose, and a 6- O -methyl-(2- O -methyl- D -galactopyranosyl)- D -galactose. At present, it is not possible to postulate a structure for the polymer.

Sulphated Polysaccharides of the Grateloupiaceae Family Part V1. A Polysaccharide from Aeodes ulvoidea

Abstract Aeodes ulvoidea , a red seaweed of the Grateloupiaceae , yielded a highly sulphated polysaccharide which was shown to contain d -galactose, 4- O -methyl-L-galactose, and 2- O -methyl- d -galactose, together with chromatographic traces of 6- O -methylgalactose, xylose, and mannose. The sulphate was not labile to alkali, but it was largely removed with methanolic hydrogen chloride. Periodate oxidation of the polysaccharide and methylation of the desulphated polymer indicate ( a ) the presence of (1→3)- and (1→4)-glycosidic links in the macromolecule, ( b ) that the 2- O -methyl- d -galactose is either (1→4)= and/or (1→3)-linked, and ( c ) that the 4- O -methyl-L-galactose is probably present only as non-reducing end-group.