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At least 433 records · Page 24Linked to original sources
PubMed2005

C-linked disaccharide analogue of the Thomsen-Friedenreich (T)-epitope alpha-O-conjugated to L-serine.

Condensation of a silylated beta-D-galactopyranosylaldehyde (3) with isolevoglucosenone (4) in the presence of Et(2)AlI provided bicyclic enone 5. Subsequent addition of BnNHOMe gave adduct 6, which was converted into 4-O-acetyl-1,6-anhydro-3-C-[(1 R)-1,3,4,5,7-penta-O-acetyl-2,6-anhydro-D-glycero-L-manno-heptitol-1-C-yl]-2-azido-2,3-dideoxy-beta-D-galacto-hexopyranose after liberation of the 2-amino group, its transformation into a 2-azido moiety, desilylation, and peracetylation. Ring-opening of the 1,6-anhydro galactopyranosyl unit and O-glycosidation with Fmoc-Ser-O-tBu afforded a 5:1 mixture of alpha- and beta-galactosides. Treatment with CH(3)COSH gave pure N-[(9H-fluoren-9-ylmethoxy)carbonyl]-{4,6-di-O-acetyl-3-C-[(1 R)-2,6-anhydro 1,3,4,5,7-penta-O-acetyl-D-glycero-L-manno-heptitol-1-C-yl]-2-[(N-acetyl)amino]-2,3-dideoxy-alpha-D-galactopyranosyl}-l-serine tert-butyl ester (2), a protected form of a C-disaccharide analogue of the Thomsen-Friedenreich (or T) epitope (beta-D-Galp-(1-->3)-alpha-D-GalNAcp) alpha-O-conjugated to L-serine.

Aldehydes↗
PubMed1997

Separation of disaccharides as their borate complexes by capillary electrophoresis with indirect detection in visible range.

Borate complexation was used to make possible the separation of disaccharides by capillary electrophoresis with indirect detection. A high borate concentration did not affect the indirect detection sensitivity in as negative a way as predicted previously. The concentration sensitivity for sucrose was determined to be 2 mM at the borate concentration of 200 mM in running electrolyte. The newly introduced background [corrected] chromophore, p-nitrophenol, allows the monitoring of the separation process in a visible range at 400 nm. This also enables the indirect detection of UV-absorbing compounds in complex mixtures in which they would be impossible to detect with a UV-absorbing background [corrected] chromophore.

Borates↗
PubMed2004

Evidence for linkage position determination in known feruloylated mono- and disaccharides using electrospray ion trap mass spectrometry.

Various feruloylated arabinose- and galactose-containing mono- and disaccharides with known linkage configurations (2-O-(trans-feruloyl)-L-arabinopyranose, 5-O-(trans-feruloyl)-L-arabinofuranose, O-[2-O-(trans-feruloyl)-alpha-L-arabinofuranosyl]-(1-->5)-L-arabinofuranose, and O-[6-O-(trans-feruloyl)-beta-D-galactopyranosyl]-(1-->4)-D-galactopyranose) were analyzed by electrospray ionization mass spectrometry using an ion trap or a quadrupole time-of-flight (Q-TOF) mass analyzer. Collision-induced dissociation (CID) experiments using the two mass analyzers generated similar tandem mass spectrometric (MS/MS) fragmentation patterns. However, the ester-bond cleavage ions were more abundant using the Q-TOF mass analyzer. Compared with the positive ion mode, the negative ion mode produces simpler and more useful CID product-ion patterns. For arabinose-containing feruloylated compounds, results obtained with both analyzers show that it is possible to assign the location of the feruloyl group to the O-2 or O-5 of arabinosyl residues. In the characterization of the 2-O-feruloyl and 5-O-feruloyl linkages, the relative abundance of the cross-ring fragment ions at m/z 265 (-60 u or -62 u after 18O-labelling) and at m/z 217 (-108 u or -110 u after 18O-labelling) play a relevant role. For galactose-containing feruloylated compounds, losses of 60, 90 and 120 Da observed in MS3 experiment correspond to the production of 0,2A1, 0,3A1 and (0,2A1-60 Da) cross-ring cleavage ions, respectively, fixing the location of feruloyl group at the O-6 of the galactose residue.

Arabinose↗
PubMed1999

Glutelin basic subunits have a mammalian mucin-type O-linked disaccharide side chain.

Characterization was done on the sugar chains of glutelin, a major storage protein in rice seeds. The basic subunits of glutelin were shown to be glycoproteins by staining with PAS and the lectins concanavalin A (Con A) and peanut agglutinin (PNA). The binding of PNA to the basic subunits was substantially reduced by treatment of the glutelin with NaIO4, NaOH, or O-glycanase. The sugar chains of the subunits, obtained by hydrazinolysis and O-glycanase, were pyridylaminated and subjected to 2-dimensional HPLC analysis using C(18) and acrylamide-derivatized columns. It was found that the Galbeta-1,3GalNAc disaccharide, which was previously identified as a core 1 structure of mucin-type sugar chains, is conjugated to the glutelin subunits. Furthermore, amino acid sequencing of an 11-kDa peptide of the subunits, recognized by both PNA and Con A, suggested that both N-linked and O-linked glycosylation occurs in the carboxy-terminal region of these subunits.

Amino Acid Sequence↗
PubMed2001

Non-disaccharide-based mechanisms of protection during drying.

Few tissues or organisms can survive the removal of nearly all their intra and extracellular water. These few have developed specialized adaptations to protect their cellular components from the damage caused by desiccation and rehydration. One mechanism, common to almost all such organisms, is the accumulation of disaccharides within cells and tissues at the onset of dehydration. This adaptation has been extensively studied and will not be considered in this review. It has become increasingly clear that true desiccation tolerance is likely to involve several mechanisms working in concert; thus, we will highlight several other important and complimentary adaptations found especially in the dehydration-resistant tissues of higher plants. These include the scavenging of reactive oxygen species, the down-regulation of metabolism, and the accumulation of certain amphiphilic solutes, proteins, and polysaccharides.

Adaptation, Physiological↗
PubMed1998

Structures of the Erythrina corallodendron lectin and of its complexes with mono- and disaccharides.

The structures of the Erythrina corallodendron lectin (EcorL) and of its complexes with galactose, N-acetylgalactosamine, lactose and N-acetyllactosamine were determined at a resolution of 1.9 to 1.95 A. The final R-values of the five models are in the range 0.169 to 0.181. The unusual, non-canonical, dimer interface of EcorL is made of beta-strands from the two monomers, which face one another in a "hand-shake" mode. The galactose molecule in the primary binding site is bound in an identical way in all four complexes. Features of the electrostatic potential of the galactose molecule match those of the potential in the combining site, thus probably pointing to the contribution of the electrostatic energy to determining the orientation of the ligand. No conformational change occurs in the protein upon binding the ligand. Subtle variations in the binding mode of the second monosaccharide (glucose in the complex with lactose and N-acetylglucosamine in the complex with N-acetyllactosamine) were observed. The mobility of Gln219 is lower in the complexes with the disaccharides than in the complexes with the monosaccharides, indicating further recruitment of this residue to ligand binding through more extensive hydrogen bonding in the former complexes. Water molecules that have been located in the combining sites of the five structures undergo rearrangement in response to binding of the different ligands. The new structural information is in qualitative agreement with thermodynamic data on the binding to EcorL.

Acetylgalactosamine↗
PubMed2000

Mechanism of hyaluronan binding and degradation: structure of Streptococcus pneumoniae hyaluronate lyase in complex with hyaluronic acid disaccharide at 1.7 A resolution.

Hyaluronic acid (HA) is an important constituent of the extracellular matrix; its bacterial degradation has been postulated to contribute to the spread of certain streptococci through tissue. Pneumococci and other streptococci produce hyaluronate lyase, an enzyme which depolymerizes HA, thus hyaluronate lyase might contribute directly to bacterial invasion. Although two different mechanisms for lyase action have been proposed, there was no crystallographic evidence to support those mechanisms. Here, we report the high-resolution crystal structure of Streptococcus pneumoniae hyaluronate lyase in the presence of HA disaccharide product, which ultimately provides the first crystallographic evidence for the binding of HA to hyaluronate lyase. This structural complex revealed a key interaction between the Streptococcus peneumoniae hyaluronate lyase protein and the product, and supports our previously proposed novel catalytic mechanism for HA degradation based on the native Streptococcus peneumoniae hyaluronate lyase structure. The information provided by this complex structure will likely be useful in the development of antimicrobial pharmaceutical agents.

Binding Sites↗
PubMed2001

Conformation of the glycosidic linkage in a disaccharide investigated by double-quantum solid-state NMR.

Double-quantum heteronuclear local field NMR is performed on a sample of a 13C2-labeled disaccharide, in which the two 13C spins are located on opposite sides of the glycosidic linkage. The evolution of the double-quantum coherences is found to be consistent with the solid-state conformation of the molecule, as previously determined by X-ray diffraction. The dependence of the double-quantum evolution on the glycosidic torsional angles is examined by using a graphical molecular manipulation program interfaced to a numerical spin simulation module.

Carbohydrate Conformation↗
PubMed1983

Inhibition of the alpha-glucosidase specific for collagen disaccharide units in diabetic rat kidney by in vivo glucose levels: possible contribution to basement membrane thickening.

The activity of the alpha-glucosidase specific for collagen disaccharide units has been measured in kidney cortex homogenates of streptozotocin-diabetic rats under three different conditions: (1) in dialyzed homogenates; (2) in non-dialyzed homogenates; (3) in non-dialyzed homogenates to which glucose was added to compensate for dilution due to homogenization and to reach the glucose concentration determined in kidney cortex (37.5 +/- 2.8 mmol/kg diabetic cortex versus 6.8 +/- 0.3 mmol/kg normal cortex). Under the latter condition, the enzyme activity was markedly decreased in diabetic kidney cortex when compared with that of normal age-matched controls: 4.03 +/- 0.25 versus 6.82 +/- 0.29 units/mg protein (p less than 0.001). Inhibition of enzyme activity was also significant in non-dialyzed diabetic homogenates without additional glucose. In the absence of glucose (in the dialyzed homogenates), it is confirmed that the enzyme activity is elevated in diabetic kidney. The glucose inhibition of the enzyme activity has been shown to be important under in vivo conditions. It may therefore contribute to kidney basement membrane thickening.

Animals↗
PubMed1994

Molecular modelling of the Dolichos biflorus seed lectin and its specific interactions with carbohydrates: alpha-D-N-acetyl-galactosamine, Forssman disaccharide and blood group A trisaccharide.

The three-dimensional structure of Dolichos biflorus seed lectin has been constructed using five legume lectins for which high resolution crystal structures were available. The validity of the resulting model has been thoroughly investigated. Final structure optimization was conducted for the lectin complexed with alpha GalNAc, providing thereby the first three-dimensional structure of lectin/GalNAc complex. The role of the N-acetyl group was clearly evidenced by the occurrence of a strong hydrogen bond between the protein and the carbonyl oxygen of the carbohydrate and by hydrophobic interaction between the methyl group and aromatic amino acids. Since the lectin specificity is maximum for the Forssman disaccharide alpha GalNAc(1-3) beta GalNAc-O-Me and the blood group A trisaccharide alpha GalNAc(1-3)[alpha Fuc(1-2)] beta Gal-O-Me, the complexes with these oligosaccharides have been also modelled.

ABO Blood-Group System↗
PubMed1995

Computer simulation of histo-blood group oligosaccharides: energy maps of all constituting disaccharides and potential energy surfaces of 14 ABH and Lewis carbohydrate antigens.

The three-dimensional structures of fourteen histo-blood groups carbohydrate antigens have been established through a combination of molecular mechanics and conformational searching methods. The conformational space available for each disaccharide, constituents of these determinants, has been throroughly characterized. The results have been organized in a data bank fashion. Larger relatives, i.e. 14 tri- and tetrasaccharides of histo-blood group antigens, have been modelled using a different method for exploring the complex potential energy surface. This approach is aimed at establishing all the possible families of conformations, along with the conformational pathways. Different conformational behaviours are exhibited by these oligosaccharides. Some of them, i.e. Le(x) and Le(y) tri and tetrasaccharides, are very rigid; 99% of their populations belong to the same conformational family. Others, like H type 1, H type 2 or H type 6 oligosaccharides, are essentially rigid, but a secondary conformational family, corresponding to 3-4% of the total population, can arise. Finally, the H types 3 and 4 trisaccharides, and the A type 1 and A type 2 tetrasaccharides are predicted to behave rather flexibly. The information gathered in the present investigation has been used to analyse the body of experimental evidence, either physical or biological, available for this series of carbohydrate antigens. Of special interest are the several different alignments that can be proposed for these molecules. They yield a realistic definition of the three-dimensional features of the epitopes thereby providing essential information about how carbohydrate antigens are recognized by proteins.

ABO Blood-Group System↗
PubMed1989

Synthesis of mono- and disaccharide amino-acid derivatives for use in solid phase peptide synthesis.

N-Fluorenylmethyloxycarbonyl-protected serine and threonine derivatives, carrying O-glycosidically alpha- or beta-linked peracetylated beta-D-Galp-(1-3)-D-GalNAcp carbohydrate chains, were prepared. These derivatives are intended for use in solid phase glycopeptide synthesis. Suitably protected mono- and disaccharide thioglycosides were used as carbohydrate intermediates. These were activated by treatment with bromine to give the glycosyl bromides, which were then used in silver triflate-promoted glycosidations of N-fluorenylmethyloxycarbonyl amino-acid phenacyl esters. Removal of the phenacyl esters with zinc gave the target free acids.

Amino Acids↗
PubMed1996

Evolution and kinetics of monosaccharides, disaccharides and alpha-galactosides during germination of lentils.

The effect of light and seed rinsing during the germination of lentil seeds (Lens culinaris var. vulgaris, cultivar Magda-20) on the level of monosaccharides, disaccharides and alpha-galactosides (raffinose, ciceritol and stachyose) was investigated. The total soluble sugar content corresponded to about 9% of the mature seed weight, about 65% of which was alpha-galactosides. Germination brought about a large decrease in alpha-galactosides: 18% to 40% losses after 3 days and 100% after 6 days. However, glucose, which was not detected in ungerminated seeds, as well as fructose and sucrose gradually increased during germination. The content of alpha-galactosides decreased more rapidly when germinating seeds were given 6 h light per day, but under these conditions there was also a major reduction in the levels of fructose, glucose and sucrose. Seeds rinsed daily showed a greater reduction of alpha-galactosides and an increase in the levels of fructose, glucose and sucrose. When seeds were germinated for 10 days in the dark with daily rinsing, the content of alpha-galactosides decreased gradually during the first 4 days and they were not detected after 6 days. Under these conditions, fructose, glucose and sucrose, which represented about 3% of the mature seed weight, started increasing after day 2 and represented more than 13% of the germinated seed dry weight after 10 days.

Disaccharides↗
PubMed2003

Enhancement of heparin and heparin disaccharide absorption by the Phytolacca americana saponins.

We studied the effects of phytolaccosides, saponins from Phytolacca americana, on the intestinal absorption of heparin in vitro and in vivo. The absorption enhancing activity of these compounds (phytolaccosides B, D2, E, F, G and I) was determined by changes in transepithelial electrical resistance (TEER) and the transport amount of heparin disaccharide, the major repeating unit of heparin, across Caco-2 cell monolayers. With the exception of phytolaccoside G, all of them decreased TEER values and increased the permeability in a dose-dependent and time-dependent manner. In vitro, phytolaccosides B, D2, and E showed significant absorption enhancing activities, while effects by phytolaccoside F and I were mild. In vivo, phytolaccoside E increased the activated partial thromboplastin time (APTT) and thrombin time, indicating that phytolaccoside E modulated the transport of heparin in intestinal route. Our results suggest that a series of phytolaccosides from Phytolacca americana can be applied as pharmaceutical excipients to improve the permeability of macromolecules and hydrophilic drugs having difficulty in absorption across the intestinal epithelium.

Adjuvants, Pharmaceutic↗
PubMed2002

Desulfobulbus mediterraneus sp. nov., a sulfate-reducing bacterium growing on mono- and disaccharides.

A new sulfate-reducing bacterium, strain 86FS1, was isolated from a deep-sea sediment in the western Mediterranean Sea with sodium lactate as electron and carbon source. Cells were ovoid, gram-negative and motile. Strain 86FS1 contained b- and c-type cytochromes. The organism was able to utilize propionate, pyruvate, lactate, succinate, fumarate, malate, alanine, primary alcohols (C(2)-C(5)), and mono- and disaccharides (glucose, fructose, galactose, ribose, sucrose, cellobiose, lactose) as electron donors for the reduction of sulfate, sulfite or thiosulfate. The major products of carbon metabolism were acetate and CO(2), with exception of n-butanol and n-pentanol, which were oxidized only to the corresponding fatty acids. The growth yield with sulfate and glucose or lactate was 8.3 and 15 g dry mass, respectively, per mol sulfate. The temperature limits for growth were 10 degrees C and 30 degrees C with an optimum at 25 degrees C. Growth was observed at salinities ranging from 10 to 70 g NaCl l(-1). Sulfide concentrations above 4 mmol l(-1) inhibited growth. The fatty acid pattern of strain 86FS1 resembled that of Desulfobulbus propionicus with n-14:0, n-16:1omega7, n-16:1 omega5, n-17:1 omega6 and n-18:1 omega7 as dominant fatty acids. On the basis of its phylogenetic position and its phenotypic properties, strain 86FS1 affiliates with the genus Desulfobulbus and is described as a new species, Desulfobulbus mediterraneus sp. nov.

Deltaproteobacteria↗
PubMed1989

Sanfilippo D syndrome: estimation of N-acetylglucosamine-6-sulfatase activity with a radiolabeled monosulfated disaccharide substrate.

N-Acetylglucosamine-6-sulfatase activity was assayed by incubation of the radiolabeled disaccharide O-(a-N-acetylglucosamine-6-sulfate)-(1----3)-L-[6-3H]-idonic acid (GlcNAc6S-IdOA), with homogenates of leucocytes, cultured fibroblasts, and urine from normal individuals, patients affected with N-acetylglucosamine-6-sulfatase-deficiency (Sanfilippo D syndrome, mucopolysaccharidosis type IIID), and patients affected with other mucopolysaccharidoses and lysosomal storage disorders. The assay clearly distinguished affected homozygotes from their obligate heterozygotes and normal controls and other lysosomal storage disorders. Sulfatase activity in fibroblasts, leucocytes, and urine toward GlcNAc6S-IdOA exhibited a pH optimum at 4.2, 4.5, and 5.1, respectively. Sulfatase activity in fibroblasts had an apparent Km of 7.2 microM and was significantly inhibited by both sulfate and phosphate ions. The action of fibroblast or leucocyte N-acetylglucosamine-6-sulfatase activity toward GlcNAc6S-IdOA is recommended for the routine enzymatic detection and classification of mucopolysaccharidosis type IIID patients.

Amnion↗
PubMed1988

Effects of sugar alcohols and disaccharides in inducing the hexagonal phase and altering membrane properties: implications for diabetes mellitus.

A number of sugars lowered the bilayer to hexagonal phase transition temperature of dielaidoylphosphatidylethanolamine. Disaccharides had the greatest effect followed by sugar alcohols. The monosaccharides, glucose and galactose had no effect on this phase transition temperature. The sugars promoted vesicle leakage only under conditions where the lipid was near its hexagonal phase transition temperature. Leakage from lipids in the bilayer state was inhibited by the sugars. Polyols, such as sorbitol, promote hexagonal phase formation and alter membrane permeability. These membrane effects may contribute to the damage caused by sorbitol accumulation in certain tissues of diabetic patients.

Calorimetry, Differential Scanning↗