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At least 307 records · Page 17Linked to original sources
PubMed2004

Synthesis, conformation, and immunogenicity of monosaccharide-centered multivalent HIV-1 gp41 peptides containing the sequence of DP178.

Several monosaccharide-centered multivalent HIV-1 gp41 peptides containing the sequence of DP178 were synthesized. Conformational studies showed that multivalent assembly enhanced the alpha-helical content of the peptide. Therefore, 2-, 3-, or 4-alpha-helix bundles of peptide DP178 could be obtained by assembling the peptide on a suitable bi-, tri-, or tetravalent template. Immunization studies indicated that while peptide DP178 alone was poorly immunogenic, the tetravalent peptide MVP-1 raised high titers of antibodies in mice that recognize not only peptide DP178 but also the native HIV-1 glycoprotein gp41, even in the absence of a carrier protein or adjuvant. The study suggests that carbohydrate-centered multivalent peptides provide not only a model for mimicking protein alpha-helix-bundle structure, but also an effective immunogen for raising high-titer antibodies against HIV-1 envelope glycoprotein gp41.

Amino Acid Sequence↗
PubMed2005

Boronic acid fluorescent sensors for monosaccharide signaling based on the 6-methoxyquinolinium heterocyclic nucleus: progress toward noninvasive and continuous glucose monitoring.

The synthesis, characterization, and spectral properties of strategically designed boronic acid containing fluorescent sensors, o-, m-, p-BMOQBA, for the potential detection of tear glucose concentrations when immobilized in plastic disposable contact lenses is described. The new probes, BMOQBAs, consist of the 6-methoxyquinolinium nucleus as a fluorescent indicator, and the boronic acid moiety as a glucose chelating group. A control compound BMOQ, which has no boronic acid group and therefore does not bind monosaccharides has also been prepared. In this paper, we show that structural design considerations of the new probes have afforded for their compatibility within the lenses, with reduced probe sugar-bound pK(a) favorable with the mildly acidic lens environment. In addition, the new probes are readily water soluble, have high quantum yields, and can be prepared by a simple one-step synthetic procedure.

Boronic Acids↗
PubMed2004

Hydrothermal upgrading of biomass to biofuel; studies on some monosaccharide model compounds.

During the hydrothermal upgrading of biomass, hydrolysis to glucose is an important step. To elucidate some of the reaction pathways that follow this initial hydrolysis, the hydrothermal treatment (340 degrees C, 27.5 MPa, 25-204 s) of dilute (50 mM) solutions of D-glucose and some other monosaccharides were studied. As a result of the increase of Kw under subcritical conditions, both acid and base catalysed reactions occur. The acid catalysed reactions are mainly dehydrations leading initially to 5-hydroxymethylfurfural. Important base catalysed reactions result in glycolaldehyde and glyceraldehyde. Further fragmentations and dehydrations lead to a variety of low molecular weight compounds such as formic acid, acetic acid, lactic acid, acrylic acid, 2-furaldehyde and 1,2,4-benzenetriol. Important pathways leading to a decrease of the O-content of the liquid reaction products start from the intermediate glyceraldehyde, which forms pyruvaldehyde, which in its turn is converted into formic acid and acetaldehyde. The latter compound can also be formed via isomerisation of glyceraldehyde into lactic acid followed by decarbonylation.

Acetaldehyde↗
PubMed2004

Kinetic and chemical studies on the isomerization of monosaccharides in N-methylmorpholine-N-oxide (NMMO) under Lyocell conditions.

The Lyocell process is a modern and environmentally fully compatible industrial fiber-making technology. Cellulosic pulp is dissolved without chemical derivatization in a melt of N-methylmorpholine-N-oxide monohydrate (NMMO). In the present work, the reactions of monosaccharides under Lyocell conditions were investigated in detail, using capillary zone electrophoresis as the analytical technique to clarify the composition of reaction mixtures and to follow the kinetics. Under Lyocell conditions, xylose and glucose undergo two competitive reactions: rapid conversion to nonreducing products, and complete isomerization involving the whole carbohydrate backbone, via ketose intermediates. Sugar acids are present in minor amounts only, as demonstrated by employing isotopically labeled material for NMR techniques.

Carbohydrate Conformation↗
PubMed2004

Indium-promoted Barbier-type allylations in aqueous media: a convenient approach to 4-C-branched monosaccharides and (1-->4)-C-disaccharides.

Starting from methyl 6-bromo-4,6-dideoxy-alpha-D-threo-4-enopyranoside, 4-C-branched sugars have been prepared through indium-promoted Barbier-type allylation of various aldehydes in aqueous media followed by hydroboration of the resulting double bond. The intermediate unsaturated monosaccharides were shown to rearrange in acidic media to give 4-C-acetyl-5-C-alkyl pyranose compounds. From beta-1-formyl sugars the corresponding beta-(1-->4)-C-disaccharides were obtained.

Allyl Compounds↗
PubMed2005

The linkage between O-specific caryan and core region in the lipopolysaccharide of Burkholderia caryophylli is furnished by a primer monosaccharide.

From the lipopolysaccharide (LPS) fraction of the plant-pathogenic bacterium Burkholderia caryophylli, the linkage between O-specific caryan and core region was characterised. The LPS fraction was first treated with 48% aqueous HF at 4 degrees C and successively with 1% acetic acid at 100 degrees C. A main oligosaccharide representing the carbohydrate backbone of the core region and a portion of the caryan (three unit of caryose) was isolated by high-performance anion-exchange chromatography. Compositional and methylation analyses, matrix-assisted laser desorption/ionisation mass spectrometry and 2D NMR spectroscopy identified the structure: [carbohydrate structure: see text]. The above residues are alpha-linked pyranose rings, if not stated otherwise. Hep is L-glycero-D-manno-heptose, Car is 4,8-cyclo-3,9-dideoxy-L-erythro-D-ido-nonose and Kdo is 3-deoxy-D-manno-oct-2-ulosonic acid. This finding indicates that QuiNAc residue is the primer monosaccharide, which connects the core oligosaccharide to caryan O-chain.

Acetic Acid↗
PubMed2006

Chlorodifluoromethyl-substituted monosaccharide derivatives--radical activation of the carbon-chlorine-bond.

The dithionite-mediated addition of BrCF(2)Cl to 3,4-di-O-pivaloyl-D-xylal (1) generated preferably 1-CF(2)Cl-substituted products, that is, (2-bromo-2-deoxy-3,4-di-O-pivaloyl-beta-D-xylopyranosyl)-chlorodifluoromethane and (2-deoxy-3,4-di-O-pivaloyl-beta-D-threo-pentopyranosyl)-chlorodifluoromethane. Selected chlorodifluoromethyl-substituted monosaccharide derivatives were hydrodechlorinated or alkylated at the CF(2)Cl-group using tin reagents under radical reaction conditions. Thus, hydrodechlorinations of (2,3,4-tri-O-acetyl-6-deoxy-alpha-L-galactopyranosyl)-chlorodifluoromethane and of methyl 3,4-di-O-acetyl-2-C-chlorodifluoromethyl-2,6-dideoxy-alpha/beta-L-glucopyranoside are reported using tri-n-butyltin hydride initiated by AIBN. UV-initiated allylations are reported for reactions of (2-deoxy-3,4-di-O-pivaloyl-beta-D-threo-pentopyranosyl)-chlorodifluoromethane, (2,3,4-tri-O-acetyl-6-deoxy-alpha-L-galactopyranosyl)-chlorodifluoromethane, 1,3,4,6-tetra-O-acetyl-2-C-chlorodifluoromethyl-2-deoxy-alpha-D-glucopyranose, 1,3,4,6-tetra-O-acetyl-2-C-chlorodifluoromethyl-2-deoxy-alpha-D-mannopyranose and methyl 3,4-di-O-acetyl-2-C-chlorodifluoromethyl-2-deoxy-alpha/beta-D-rabinopyranoside with allyltri-n-butyltin.

Carbon↗
PubMed2006

Beta-propeller crystal structure of Psathyrella velutina lectin: an integrin-like fungal protein interacting with monosaccharides and calcium.

The lectin from the mushroom Psathyrella velutina recognises specifically N-acetylglucosamine and N-acetylneuraminic acid containing glycans. The crystal structure of the 401 amino acid residue lectin shows that it adopts a very regular seven-bladed beta-propeller fold with the N-terminal region tucked into the central cavity around the pseudo 7-fold axis. In the complex with N-acetylglucosamine, six monosaccharides are bound in pockets located between two consecutive propeller blades. Due to the repeats shown by the sequence the binding sites are very similar. Five hydrogen bonds between the protein and the sugar hydroxyl and N-acetyl groups stabilize the complex, together with the hydrophobic interactions with a conserved tyrosine and histidine. The complex with N-acetylneuraminic acid shows molecular mimicry with the same hydrogen bond network, but with different orientations of the carbohydrate ring in the binding site. The beta-hairpin loops connecting the two inner beta-strands of each blade are metal binding sites and two to three calcium ions were located in the structure. The multispecificity and high multivalency of this mushroom lectin, combined with its similarity to the extracellular domain of an important class of cell adhesion molecules, integrins, are another example of the outstanding success of beta-propeller structures as molecular binding machines in nature.

Acetylglucosamine↗
PubMed2002

Biophysical characterization of triacyl monosaccharide lipid a partial structures in relation to bioactivity.

Synthetic triacyl glucosamine monosaccharide lipid A part structures corresponding to the non-reducing moiety of enterobacterial lipid A with an acyloxyacyl chain linked to position 3 of the glucosamine and an unbranched chain linked to position 2 (group 1) and vice versa (group 2) were analyzed biophysically: Fourier-transform infrared spectroscopy was performed to characterize the gel-to-liquid crystalline phase transition, the phosphate band contour, and the orientation of the glucosamine with respect to the membrane surface. Small-angle x-ray diffraction was applied for the elucidation of the supramolecular aggregate structure and, with that, of the molecular shape. With fluorescence resonance energy transfer the lipopolysaccharide-binding protein (LBP)-mediated intercalation of the lipid A partial structures into phospholipid liposomes was monitored. The physical data clearly exhibit a classification of the synthetic compounds into two groups: group 1 compounds have sharp phase transitions, indicating dense acyl chain packing and an inclination of the glucosamine backbone with respect to the membrane surface of 30 degrees with the phosphate buried in the membrane. Group 2 compounds have a very broad phase transition, indicating poorly packed acyl chains, and an inclination of -30 degrees with the phosphate group sticking outward. For the first group unilamellar phases are observed superimposed by a non-lamellar structure, and for the second one only multilamellar aggregate structures. The cytokine-inducing capacity in human mononuclear cells is relatively high for the first group and low or absent for the second group. Based on these data a model of the intra and intermolecular conformations is proposed which also extends the concept of "endotoxic conformation."

Animals↗
PubMed1968

The kinetics of selective biological transport. 3. Erythrocyte-monosaccharide transport data.

The simplest biological transport system so far extensively investigated is that of monosaccharides in human erythrocytes. Despite its simplicity there is still considerable doubt and divergence of opinion concerning its mechanism. Some confusion may arise as a result of the comparison of diverse data obtained by different workers using a variety of experimental techniques. To minimize this problem, an attempt is made here to repeat, under standard conditions and with as much care as possible, five of the more definitive types of experiments previously performed on this system. It is hoped that the result of this effort is an internally consistent set of data with which the quantitative predictions of various proposed mechanisms may be compared as a primary criterion for their acceptability.

Biological Transport↗
PubMed1968

The kinetics of selective biological transport. IV. Assessment of three carrier systems using the erythrocyte-monosaccharide transport data.

An assessment is made of the possible validity of three transport mechanisms proposed to describe the movement of monosaccharides in human erythrocytes. These mechanisms consist of a simple carrier system and two mechanisms derived from it, one of which postulates that the free carrier moves more slowly than the complexed carrier, and the other that slow diffusion steps occur at each surface of the membrane. None of these schemes provides an adequate quantitative description of the data so that all must be discarded, leaving the question of the mechanism still open to speculation.

Biological Transport↗
PubMed2000

Volumetric properties for the monosaccharide (D-xylose, D-arabinose, D-glucose, D-galactose)-NaCl-water systems at 298.15 K.

Densities have been measured for monosaccharide (D-xylose, D-arabinose, D-glucose and D-galactose)-NaCl-water solutions at 298.15 K. These data have been used to determine the apparent molar volumes of these saccharides and NaCl in the studied solutions. Infinite-dilution apparent molar volumes for the saccharides (V0(phi,S)) in aqueous NaCl and those for NaCl (V0(phi,E)) in aqueous saccharide solutions have been evaluated, together with the standard transfer volumes of the saccharides (delta(t) V0S) from water to aqueous NaCl and of NaCl (delta(t) V0E) from water to aqueous saccharide solutions. It is shown that the delta(t) V0S and delta (t) V0E values are positive and increase with increasing co-solute molalities. Volumetric parameters indicating the interactions of NaCl with saccharides in water have been obtained, respectively, by using transfer volumes of the saccharides and NaCl, and the resulting values are in good agreement with each other within experimental error. The interactions between saccharides and NaCl are discussed in terms of the structural interaction model and the stereochemistry of the saccharide molecules in water.

Arabinose↗
PubMed1994

A reversed phase HPLC method for the simultaneous determination of all monosaccharides contained in galactosaminoglycan isomers from human aorta proteoglycans.

Monosaccharides obtained by reduction and hydrolysis of galactosaminoglycan isomers, are entirely determined as their perbenzoyl derivatives by reversed phase HPLC, without removal of hexosamines prior to benzoylation. The method is suitable for the analysis of arterial proteoglycan constituent galactosaminoglycans, providing specific, precise and reproducible results. Moreover, synthesis and characterization of tri-O-benzoyl-1,6-L-anhydroidose and N-benzoyl-tetra-O-benzoyl-alpha- and -beta-D-galactosamine have been accomplished.

Adult↗
PubMed2001

Synthesis of derivatives of C-nucleoside analogues using 'push-pull' functionalized monosaccharides.

7-Deoxy-1,2:3,4-di-O-isopropylidene-alpha-D-galacto-heptopyranos-6-ulose (1) reacted with carbon disulphide and methyl iodide in the presence of a base to furnish 7,8-dideoxy-1,2:3,4-di-O-isopropylidene-8,8-[bis(methylthio)]-alpha-D-galacto-oct-7-enopyranos-6-ulose (2). This 'push-pull' activated unsaturated monosaccharide underwent a ring closure reaction with hydrazine hydrate to give the 'inversed' C-nucleoside analogue 3. Compound 1 and malononitrile yielded the 7-cyano-6,7-dideoxy-1,2:3,4-di-O-isopropylidene-6-methyl-alpha-D-galacto-oct-6-enopyranurononitrile (4). Treatment of 4 with carbon disulphide and methyl iodide in the presence of a base afforded the sugar 'push-pull' butadiene 5 which was transformed into the pyridine nucleoside analogue 6.

Antineoplastic Agents↗
PubMed1998

Studies towards neoglycoconjugates from the monosaccharide determinant of Vibrio cholerae O:1, serotype Ogawa using the diethyl squarate reagent.

The effect of reaction time, concentration and molar excess of hapten upon the efficiency of the conjugation of carbohydrates to proteins using the diethyl squarate reagent has been studied using chicken serum albumin (CSA) as the carrier protein and a linker-equipped D-glucose derivative as the hapten. A high degree of incorporation of the latter into CSA was achieved with high efficiency, and the use of a large excess of the ligand was not necessary. Conjugation of the immunodominant monosaccharide determinant of Vibrio cholerae O:1, serotype Ogawa, bearing the same spacer, followed a similar pattern, showing that the nature of the carbohydrate does not substantially affect the outcome of the conjugation and that a predicted degree of antigen-loading onto carrier protein is possible to achieve.

Animals↗
PubMed2000

Thermotropic and lyotropic properties of long chain alkyl glycopyranosides. Part I: monosaccharide headgroups.

A systematic structure variation of a classical amphiphile (dodecyl-beta-D-glucopyranoside) is performed, demonstrating the influence of anomeric linkage, configuration, ring size and flexibility as well as electric charges on the mesophase behaviour. In addition, we have investigated the thermotropic and lyotropic properties of some long chain alkyl glycosides with monosaccharide headgroups. The thermotropism was measured with polarizing microscopy and differential scanning calorimetry, and additionally the lyotropism with FTIR spectroscopy and X-ray diffraction.

Calorimetry, Differential Scanning↗
PubMed1987

High-performance liquid chromatographic isolation of 14C-labelled gluco-oligosaccharides, monosaccharides and sugar degradation products on ion-exchange resins.

Gluco-oligosaccharides, monosaccharides and sugar degradation products in biomass hydrolysates were isolated in milligram amounts by means of high-performance liquid chromatography on various ion-exchange stationary phases. Also, radioactively labelled carbohydrates and sugar decomposition products that had been obtained on hydrolysis of 14C-marked biomass were isolated and are thus available as reference samples.

Carbohydrates↗