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Disaccharides
Terms modified by Disaccharides Selected AbstractsSolution Synthesis of Two Orthogonally Protected Lactosides as Tetravalent Disaccharide-Based ScaffoldsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 13 2004Sergio Castoldi Abstract Two tetravalent lactosidic scaffolds have been synthesised in solution from commercial lactose. Careful manipulation of the protecting groups allowed us to orthogonally protect four OH groups for their use as diversity sites for the development of broad screening libraries of sugar mimics. The selective access to each of these hydroxy groups has been demonstrated on scaffold 2 by deprotection and functionalisation with p -fluorophenyl isocyanate. Finally, the 6-OH derivative of compound 2 was covalently attached to a polymeric support. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Design, Synthesis, and Screening of a Library of Peptidyl Bis(Boroxoles) as Oligosaccharide Receptors in Water: Identification of a Receptor for the Tumor Marker TF-Antigen Disaccharide,ANGEWANDTE CHEMIE, Issue 8 2010Arnab Pal Mini-Lectine: Eine neue Klasse von Oligosaccharid-Rezeptoren wurde entworfen (siehe Beispiel), indem mehrere Arten von molekularer Erkennung genutzt wurden, darunter die besondere Fähigkeit von Benzoboroxolen zur Komplexierung von Hexopyranosiden. Die Synthese ist modular und eignet sich deshalb besonders gut für den Aufbau kombinatorischer Bibliotheken zur Identifizierung spezifischer Oligosaccharide. [source] Hydrogen Atom Transfer Experiments Provide Chemical Evidence for the Conformational Differences between C - and O -DisaccharidesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 27 2010Elisa I. León Abstract The glycopyran-6- O -yl radical promoted hydrogen atom transfer reaction (HAT) between the two pyranose units of ,- D -Manp -(1,4)-,- D -Glcp and ,- D -Manp -(1,4a)-4a-carba-,- D -Glcp disaccharides provides supporting chemical evidence for the conformational differences between O - and C -glycosyl compounds. In the O -disaccharide the 6-alkoxyl radical, generated under oxidative or reductive conditions, abstracts exclusively the hydrogen at C-5, via a completely regioselective 1,8-HAT reaction. This may be attributable to the conformational restriction of the glycosidic and aglyconic bonds due principally to steric and stereoelectronic effects. On the contrary, very little regioselectivity is observed in the homologous C -disaccharide and a mixture of compounds generated by 1,5-, 1,6-, and 1,8-HAT processes where the abstraction occurs at hydrogen atoms positioned at C-4a, C-1,, and C-5,, respectively, has been obtained. This study has been extended to simpler O - and C -glycosides, where the aglycon was a straight n -alkyl alcohol tether of five atoms; in general, all of the results obtained are shown to be consistent with a major conformational flexibility of the C -glycosidic bond. [source] Synthesis of a New Type of Glycosidic Linkage: Acetal-Linked Disaccharides and Trisaccharides of Acyclic and Cyclic Sugars,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 15 2005Soni Kamlesh Madhusudan Abstract New types of di- and trisaccharides related to a unique trisaccharide present in the cell walls of Proteus have been synthesized by coupling of acyclic sugar dithioacetals and di- and monohydroxy cyclic sugars. In this class of compounds an acyclic sugar is linked to a cyclic sugar through an acetal linkage. The formation of these acetal-linked pseudodi- and-trisaccharides has been achieved by a generalized reaction procedure mediated by 1,3-dibromo-5,5-dimethylhydantoin under mild, metal-free and neutral conditions. Sixteen protected and twelve deprotected di- and trisaccharides related to the trisaccharide found in the Proteus cell wall have been synthesized. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Linkage position and residue identification of disaccharides by tandem mass spectrometry and linear discriminant analysisRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 10 2008Hui Zhang The discrimination of isomeric disaccharides with different linkage types and different monosaccharide residues , glucose (Glc), galactose (Gal), and mannose (Man) at the non-reducing end , was investigated with tandem mass spectrometry (MS/MS) and linear discriminant analysis (LDA). Conventional matrix-assisted laser desorption/ionization (MALDI)-MS has strong interference peaks from matrix ions in the low mass region (<500,Da). This greatly limits the application of MALDI-MS for the analysis of small molecules such as saccharides. We solved this problem by using LDI with acidic fullerene matrix, which gives a very clean background in the low-mass region. Disaccharides with different linkage types give different tandem mass spectral profiles from various cross-ring fragmentation pathways. Disaccharides with the same linkage type but with three different kinds of monosaccharide residues bear the same fragmentation profiles. However, the relative ratios of the fragment ion intensities were found to be distinctly different among the three disaccharide isomers. By employing statistical tools such as LDA to classify the tandem mass spectra, disaccharide isomers with either different linkages or different monosaccharide residues were successfully classified. Copyright © 2008 John Wiley & Sons, Ltd. [source] 1,3-Dipolar Cycloaddition of exo-Methylenesugars with Nitrone: Approach to New Amino-C-ketosyl Disaccharides.CHEMINFORM, Issue 35 2004Xiaoliu Li Abstract For Abstract see ChemInform Abstract in Full Text. [source] A Simplified Ramberg,Baecklund Approach to Novel C-Glycosides and C-Linked Disaccharides.CHEMINFORM, Issue 29 2003Graeme D. McAllister Abstract For Abstract see ChemInform Abstract in Full Text. [source] One-Pot Synthesis of Multivalent Arrays of Mannose Mono- and Disaccharides.CHEMINFORM, Issue 4 2003Wayne Hayes Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: N-Glycyl-,-glycopyranosylamines, Derivatives of Mono- and Disaccharides, and Their Use for the Preparation of Carboxylic Acid Glycoconjugates.CHEMINFORM, Issue 6 2001L. M. Likhosherstov Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Integrated Enzymatic Synthesis and Adsorption of Isomaltose in a Multiphase Fluidized Bed ReactorENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 5 2006M. Ergezinger Abstract Dextransucrase catalyzes the formation of dextran, but also of numerous oligosaccharides from sucrose and different acceptors, if appropriate conditions are chosen. A process on a technical scale with immobilized enzyme was established to produce isomaltose, a disaccharide of industrial interest. Isomaltose is also a reactant for dextransucrase and has to be quickly taken out of the reaction solution. This was realized by integrated adsorption of isomaltose on zeolites. In the case of biotransformation the reactor works with a fluidized bed of immobilized enzyme and the in situ separation is realized with a suspension flow of adsorbent. This process was investigated experimentally and theoretically. With a design model consisting of hydrodynamics, kinetics of enzymatic synthesis, and thermodynamics of adsorption, a comparison was made between experimental and calculated data. [source] A disaccharide derived from chondroitin sulphate proteoglycan promotes central nervous system repair in rats and mice,EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 8 2004Asya Rolls Abstract Chondroitin sulphate proteoglycan (CSPG) inhibits axonal regeneration in the central nervous system (CNS) and its local degradation promotes repair. We postulated that the enzymatic degradation of CSPG generates reparative products. Here we show that an enzymatic degradation product of CSPG, a specific disaccharide (CSPG-DS), promoted CNS recovery by modulating both neuronal and microglial behaviour. In neurons, acting via a mechanism that involves the PKC, and PYK2 intracellular signalling pathways, CSPG-DS induced neurite outgrowth and protected against neuronal toxicity and axonal collapse in vitro. In microglia, via a mechanism that involves ERK1/2 and PYK2, CSPG-DS evoked a response that allowed these cells to manifest a neuroprotective phenotype ex vivo. In vivo, systemically or locally injected CSPG-DS protected neurons in mice subjected to glutamate or aggregated ,-amyloid intoxication. Our results suggest that treatment with CSPG-DS might provide a way to promote post-traumatic recovery, via multiple cellular targets. [source] Hydrogen Atom Transfer Experiments Provide Chemical Evidence for the Conformational Differences between C - and O -DisaccharidesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 27 2010Elisa I. León Abstract The glycopyran-6- O -yl radical promoted hydrogen atom transfer reaction (HAT) between the two pyranose units of ,- D -Manp -(1,4)-,- D -Glcp and ,- D -Manp -(1,4a)-4a-carba-,- D -Glcp disaccharides provides supporting chemical evidence for the conformational differences between O - and C -glycosyl compounds. In the O -disaccharide the 6-alkoxyl radical, generated under oxidative or reductive conditions, abstracts exclusively the hydrogen at C-5, via a completely regioselective 1,8-HAT reaction. This may be attributable to the conformational restriction of the glycosidic and aglyconic bonds due principally to steric and stereoelectronic effects. On the contrary, very little regioselectivity is observed in the homologous C -disaccharide and a mixture of compounds generated by 1,5-, 1,6-, and 1,8-HAT processes where the abstraction occurs at hydrogen atoms positioned at C-4a, C-1,, and C-5,, respectively, has been obtained. This study has been extended to simpler O - and C -glycosides, where the aglycon was a straight n -alkyl alcohol tether of five atoms; in general, all of the results obtained are shown to be consistent with a major conformational flexibility of the C -glycosidic bond. [source] Synthesis and Biological Evaluation of Non-Hydrolyzable 1,2,3-Triazole-Linked Sialic Acid Derivatives as Neuraminidase InhibitorsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 16 2009Michel Weïwer Abstract ,-Sialic acid azide 1 has been used as a substrate for the efficient preparation of 1,2,3-triazole derivatives of sialic acid using the copper-catalyzed azide,alkyne Huisgen cycloaddition ("click chemistry"). Our approach is to generate non-natural N-glycosides of sialic acid that are resistant to neuraminidase-catalyzed hydrolysis as opposed to the natural O-glycosides. These N-glycosides would act as neuraminidase inhibitors to prevent the release of new virions. As a preliminary study, a small library of 1,2,3-triazole-linked sialic acid derivatives has been synthesized in 71,89,% yield. A disaccharide mimic of sialic acid has also been prepared using the ,-sialic acid azide 1 and a C-8 propargyl sialic acid acceptor in 68,% yield. A model sialic acid coated dendrimer was also synthesized from a perpropargylated pentaerythritol acceptor. These novel sialic acid derivatives were then evaluated as potential neuraminidase inhibitors using a 96-well plate fluorescence assay; micromolar IC50 values wereobserved, comparable to the known sialidase inhibitorNeu5Ac2en.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Structure of a 2-aminoethyl phosphate-containing O-specific polysaccharide of Proteus penneri 63 from a new serogroup O68FEBS JOURNAL, Issue 2 2000Aleksander S. Shashkov Lipopolysaccharide of Proteus penneri strain 63 was degraded by mild acid to give a high molecular mass O-specific polysaccharide that was isolated by gel-permeation chromatography. Sugar and methylation analyses and NMR spectroscopic studies, including two-dimensional 1H,1H COSY, TOCSY rotating-frame NOE spectroscopy, H-detected 1H,13C and 1H,31P heteronuclear multiple-quantum coherence (HMQC), and 1H,13C HMQC-TOCSY experiments, demonstrated the following structure of the polysaccharide: where FucNAc is 2-acetamido-2,6-dideoxygalactose and PEtn is 2-aminoethyl phosphate. The polysaccharide studied shares some structural features, such as the presence of d -GlcNAc6PEtn and an ,- L -FucNAc-(1,3)- d -GlcNAc disaccharide, with other Proteus O-specific polysaccharides. A marked cross-reactivity of P. penneri 63 O-antiserum with P. vulgaris O12 was observed and substantiated by a structural similarity of the O-specific polysaccharides of the two strains. In spite of this, the polysaccharide of P. penneri 63 has the unique structure among Proteus O-antigens, and therefore a new, separate serogroup, O68, is proposed for this strain. [source] Synthesis of a Fusion-Isomeric Cellobionoimidazole and Its Evaluation against the syn -Protonating Glycosidase Cel7AHELVETICA CHIMICA ACTA, Issue 12 2005Narinder Mohal The fusion-isomeric cellobinoimidazole 2, a potential inhibitor of the syn -protonating , -glycosidase Cel7A, was synthesised by Koenigs,Knorr glycosylation of the ,- D -arabinopyranoside 32, followed by selective hydrolysis. Glycosylation of 32 with acetobromoglucose 6 proceeded with poor diastereoselectivity, giving the desired 1,3-linked , - d- disaccharide 35 as minor product, besides the major 1,3-linked ,- d- disaccharide 36. Hg2+ -Promoted glycosylation of 32 led predominantly to the 1,2-ortho ester 33. Sequential removal of the silyl, acetyl, and allyl groups of 35 led to a 45,:,55 equilibrium mixture 2 and the manno -configured isomer 39. Similarly, deprotection of 36 gave a mixture of the maltonoimidazole 42 and the manno -configured isomer 43. According to a known protocol, the glycosyl acceptor 32 was synthesised in eleven steps and an overall yield of 8,13% from D -lyxose. The silylated arabinopyranosyl moiety of the ,- d- glucosides 13,19, 33, 34, and 36 adopts a 4C1 conformation, while the arabinopyranosyl moiety of the , - d- glucosides 17 and 35 exists as a 1,:,3,mixture of 4C1 and 1C4 conformers, as a result of the combined preferred axial orientation of bulky vicinal substituents and the anomeric effect. MM3* Modelling evidences a preferred 4C1 conformation of 35 and 36, and stronger steric interactions between the pyranosyl moieties of 35. The equilibrium mixture 2/39 proved a poor inhibitor of Cel7A with an IC50 value of ca. 4,mM. [source] Effect of trehalose on survival of Bradyrhizobium japonicum during desiccationJOURNAL OF APPLIED MICROBIOLOGY, Issue 3 2003J.G. Streeter Abstract Aims: A major reason for the ineffectiveness of legume inoculants in the field is the rapid death of rhizobia because of desiccation. The major purpose of this study was to identify conditions under which ,,, -trehalose would improve survival of Bradyrhizobium japonicum during desiccation. Methods and Results: Trehalose was added to cultures just prior to desiccation or was supplied to bacteria during the 6-day growth period. A wide variety of trehalose concentrations was tested. Trehalose added to cultures at the time of desiccation improved survival slightly, but trehalose loading during growth was much more effective in protection against desiccation. Growth of bacteria with 3 mmol l,1 trehalose increased trehalose concentration in cells by about threefold and increased survival of cells placed on soya bean [Glycine max (L.) Merr.] seeds by two- to four-fold after 2 or 24 h. Average of overall results indicate that growth of bacteria with trehalose in the medium resulted in a 294% increase in survival after 24 h of desiccation. The concentration of trehalose in cells was very highly correlated with survival of bacteria. When trehalose-loaded cells were suspended in buffer or water, 60,85% of cellular trehalose was lost in about 1 h and, in spite of these losses, survival during desiccation was not reduced. Conclusions: Accumulation of trehalose in the cytoplasm is critical to the survival of B. japonicum during desiccation. Increasing the periplasmic concentration of trehalose is also beneficial but is not so critical as the concentration of trehalose in the cytoplasm. Because B. japonicum cannot utilize trehalose as a carbon source, cells can be loaded with trehalose by providing the disaccharide during the growth period. Significance and Impact of the Study: Although it may not be practical to use trehalose as a carbon source in inoculant production, it may be possible to engineer greater trehalose accumulation in rhizobia. Trehalose concentration in cells should be a useful predictor of survival during desiccation. [source] Structures and energies of D -galactose and galabiose conformers as calculated by ab initio and semiempirical methodsJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 7 2003Majda Rahal-Sekkal Abstract Optimized geometries and total energies of some conformers of ,- and ,- D -galactose have been calculated using the RHF/6-31G* ab initio method. Vibrational frequencies were computed at the 6-31G* level for the conformers that favor internal hydrogen bonding, in order to evaluate their enthalpies, entropies, Gibbs free energies, and then their structural stabilities. The semiempirical AM1, PM3, MNDO methods have also been performed on the conformers GG, GT, and TG of ,- and ,- D -galactose. In order to test the reliability of each semiempirical method, the obtained structures and energies from the AM1, PM3, and MNDO methods have been compared to those achieved using the RHF/6-31G* ab initio method. The MNDO method has not been investigated further, because of the large deviation in the structural parameters compared with those obtained by the ab initio method for the galactose. The semiempirical method that has yielded the best results is AM1, and it has been chosen to perform structural and energy calculations on the galabiose molecule (the disaccharides constituted by two galactose units , 1,4 linked). The goal of such calculations is to draw the energy surface maps for this disaccharide. To realize each map, 144 different possible conformations resulting from the rotations of the two torsional angles , and , of the glycosidic linkage are considered. In each calculation, at each increment of , and ,, using a step of 30° from 0 to 330°, the energy optimization is employed. In this article, we report also calculations concerning the galabiose molecule using different ab initio levels such as RHF/6-31G*, RHF/6-31G**, and B3Lyp/6-31G*. © 2003 Wiley Periodicals, Inc. J Comput Chem 24: 806,818, 2003 [source] Trehalose extends longevity in the nematode Caenorhabditis elegansAGING CELL, Issue 4 2010Yoko Honda Summary Trehalose is a disaccharide of glucose found in diverse organisms and is suggested to act as a stress protectant against heat, cold, desiccation, anoxia, and oxidation. Here, we demonstrate that treatment of Caenorhabditis elegans with trehalose starting from the young-adult stage extended the mean life span by over 30% without any side effects. Surprisingly, trehalose treatment starting even from the old-adult stage shortly thereafter retarded the age-associated decline in survivorship and extended the remaining life span by 60%. Demographic analyses of age-specific mortality rates revealed that trehalose extended the life span by lowering age-independent vulnerability. Moreover, trehalose increased the reproductive span and retarded the age-associated decrease in pharyngeal-pumping rate and the accumulation of lipofuscin autofluorescence. Trehalose also enhanced thermotolerance and reduced polyglutamine aggregation. These results suggest that trehalose suppressed aging by counteracting internal or external stresses that disrupt protein homeostasis. On the other hand, the life span-extending effect of trehalose was abolished in long-lived insulin/IGF-1-like receptor (daf-2) mutants. RNA interference-mediated inactivation of the trehalose-biosynthesis genes trehalose-6-phosphate synthase-1 (tps-1) and tps-2, which are known to be up-regulated in daf-2 mutants, decreased the daf-2 life span. These findings indicate that a reduction in insulin/IGF-1-like signaling extends life span, at least in part, through the aging-suppressor function of trehalose. Trehalose may be a lead compound for potential nutraceutical intervention of the aging process. [source] Characterization of the glycosidic linkage of underivatized disaccharides by interaction with Pb2+ ionsJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 8 2007Ahlam El Firdoussi Abstract Electrospray ionization in combination with tandem mass spectrometry and lead cationization is used to characterize the linkage position of underivatized disaccharides. Lead(II) ions react mainly with disaccharides by proton abstraction to generate [Pb(disaccharide)m, H]+ ions (m = 1,2). At low cone voltages, an intense series of doubly charged ions of general formula [Pb(disaccharide)n]2+ are also observed. Our study shows that MS/MS experiments have to be performed to differentiate Pb2+ -coordinated disaccharides. Upon collision, [Pb(disaccharide) , H]+ species mainly dissociate according to glycosidic bond cleavage and cross-ring cleavages, leading to the elimination of CnH2nOn neutrals (n = 2,4). The various fragmentation processes allow the position of the glycosidic bond to be unambiguously located. Distinction between glc-glc and glc-fru disaccharides also appears straightforward. Furthermore, for homodimers of D -glucose our data demonstrate that the anomericity of the glycosidic bond can be characterized for the 1 , n linkages (n = 2, 4, 6). Consequently, Pb2+ cationization combined with tandem mass spectrometry appears particularly useful to identify underivatized disaccharides. Copyright © 2007 John Wiley & Sons, Ltd. [source] Activation of phospholipase C pathways by a synthetic chondroitin sulfate-E tetrasaccharide promotes neurite outgrowth of dopaminergic neuronsJOURNAL OF NEUROCHEMISTRY, Issue 2 2007Naoki Sotogaku Abstract In dopaminergic neurons, chondroitin sulfate (CS) proteoglycans play important roles in neuronal development and regeneration. However, due to the complexity and heterogeneity of CS, the precise structure of CS with biological activity and the molecular mechanisms underlying its influence on dopaminergic neurons are poorly understood. In this study, we investigated the ability of synthetic CS oligosaccharides and natural polysaccharides to promote the neurite outgrowth of mesencephalic dopaminergic neurons and the signaling pathways activated by CS. CS-E polysaccharide, but not CS-A, -C or -D polysaccharide, facilitated the neurite outgrowth of dopaminergic neurons at CS concentrations within the physiological range. The stimulatory effect of CS-E polysaccharide on neurite outgrowth was completely abolished by its digestion into disaccharide units with chondroitinase ABC. Similarly to CS-E polysaccharide, a synthetic tetrasaccharide displaying only the CS-E sulfation motif stimulated the neurite outgrowth of dopaminergic neurons, whereas a CS-E disaccharide or unsulfated tetrasaccharide had no effect. Analysis of the molecular mechanisms revealed that the action of the CS-E tetrasaccharide was mediated through midkine-pleiotrophin/protein tyrosine phosphatase , and brain-derived neurotrophic factor/tyrosine kinase B receptor pathways, followed by activation of the two intracellular phospholipase C (PLC) signaling cascades: PLC/protein kinase C and PLC/inositol 1,4,5-triphosphate/inositol 1,4,5-triphosphate receptor signaling leading to intracellular Ca2+ concentration-dependent activation of Ca2+/calmodulin-dependent kinase II and calcineurin. These results indicate that a specific sulfation motif, in particular the CS-E tetrasaccharide unit, represents a key structural determinant for activation of midkine, pleiotrophin and brain-derived neurotrophic factor-mediated signaling, and is required for the neuritogenic activity of CS in dopaminergic neurons. [source] Lactulose as a food ingredientJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 12 2009Agustín Olano Abstract Lactulose is a synthetic ketose disaccharide that can be obtained from lactose by different methods of synthesis. Chemical methods are based on the isomerization of lactose in the presence of basic catalysts and enzymatic methods using lactose as a galactose donor and fructose as an acceptor. The prebiotic properties of lactulose have been known for more than 50 years and numerous studies have confirmed several health benefits of lactulose as a food ingredient, including selective stimulation of intestinal flora, laxative effect and improvement of calcium absorption. Its use in fermented milk manufacture may reduce the incubation period and favour the growth of bifidobacteria. The synthesis of lactulose-derived oligosaccharides may provide a new group of prebiotics with properties complementary to those of native lactulose. Copyright © 2009 Society of Chemical Industry [source] Review article: fructose malabsorption and the bigger pictureALIMENTARY PHARMACOLOGY & THERAPEUTICS, Issue 4 2007P. R. GIBSON Summary Fructose is found widely in the diet as a free hexose, as the disaccharide, sucrose and in a polymerized form (fructans). Free fructose has limited absorption in the small intestine, with up to one half of the population unable to completely absorb a load of 25 g. Average daily intake of fructose varies from 11 to 54 g around the world. Fructans are not hydrolysed or absorbed in the small intestine. The physiological consequences of their malabsorption include increasing osmotic load, providing substrate for rapid bacterial fermentation, changing gastrointestinal motility, promoting mucosal biofilm and altering the profile of bacteria. These effects are additive with other short-chain poorly absorbed carbohydrates such as sorbitol. The clinical significance of these events depends upon the response of the bowel to such changes; they have a higher chance of inducing symptoms in patients with functional gut disorders than asymptomatic subjects. Restricting dietary intake of free fructose and/or fructans may have durable symptomatic benefits in a high proportion of patients with functional gut disorders, but high quality evidence is lacking. It is proposed that confusion over the clinical relevance of fructose malabsorption may be reduced by regarding it not as an abnormality but as a physiological process offering an opportunity to improve functional gastrointestinal symptoms by dietary change. [source] The effect of IVX-0142, a heparin-derived hypersulfated disaccharide, on the allergic airway responses in asthmaALLERGY, Issue 9 2008M. Duong Background:, IVX-0142 is a heparin-derived hypersulfated disaccharide devoid of anticoagulant activity while possessing anti-allergic and anti-inflammatory activity in preclinical studies. In a proof-of-concept study, the allergen inhalation challenge model was used to investigate the effect of IVX-0142 in mild atopic asthma. Methods:, Nineteen subjects, not on controller medications, were randomized to an evaluator-blind, placebo-controlled, cross-over study. The effect of a single nebulized dose of IVX-0142 (80 mg) or placebo administered 30 min prior to allergen inhalation was evaluated on the allergic airway responses, airway responsiveness, and airway inflammation. Results:, When compared with placebo, 14 and 13 subjects experienced a relatively smaller maximum fall in forced expiratory volume in 1 s (maxFEV1%) for the early airway response (EAR) and late airway response (LAR) with IVX-0142, respectively (P < 0.01). The degree of attenuation in the EAR [maxFEV1% (mean ± SE) 26.5 ± 2.8%vs placebo 31.0 ± 2.8%, P = 0.059] and LAR (15.6 ± 2.9%vs placebo 19.0 ± 2.9%, P = 0.24) with IVX-0142, however, was small and did not reach statistical significance compared with placebo. Similarly, a trend in the attenuation of allergen-induced increase in the absolute sputum cell counts was also observed. No difference in the allergen-induced increase in airway hyper-responsiveness and exhaled nitric oxide was noticed. Conclusions:, The majority of mild atopic asthmatics demonstrated a reduction in the EAR and LAR to IVX-0142. However, the treatment effect observed with a single prechallenge dose of IVX-0142 was small and heterogeneous. The potential anti-allergic and anti-inflammatory effects using multiple higher doses need to be evaluated. [source] Sucrose metabolism contributes to in vivo fitness of Streptococcus pneumoniaeMOLECULAR MICROBIOLOGY, Issue 1 2007Ramkumar Iyer Summary We characterized two sucrose-metabolizing systems ,sus and scr, and describe their roles in the physiology and virulence of Streptococcus pneumoniae in murine models of carriage and pneumonia. The sus and scr systems are regulated by LacI family repressors SusR and ScrR respectively. SusR regulates an adjacent ABC transporter (susT1/susT2/susX) and sucrose-6-phosphate (S-6-P) hydrolase (susH). ScrR controls an adjacent PTS transporter (scrT), fructokinase (scrK) and second S-6-P hydrolase (scrH). sus and scr play niche-specific roles in virulence. The susH and sus locus mutants are attenuated in the lung, but dispensable in nasopharyngeal carriage. Conversely, the scrH and scr locus mutants, while dispensable in the lung, are attenuated for nasopharyngeal colonization. The scrH/susH double mutant is more attenuated than scrH in the nasopharynx, indicating SusH can substitute in this niche. Both systems are sucrose-inducible, with ScrH being the major in vitro hydrolase. The scrH/susH mutant does not grow on sucrose indicating that sus and scr are the only sucrose-metabolizing systems in S. pneumoniae. We propose a model describing hierarchical regulation of the scr and sus systems by the putative inducer, S-6-P. The transport and metabolism of sucrose or a related disaccharide thus contributes to S. pneumoniae colonization and disease. [source] Formulation of aqueous concentrated alumina suspensions.POLYMER INTERNATIONAL, Issue 4 2003Influence of a disaccharide: trehalose Abstract Trehalose, a disaccharide, is very well known to protect living cells efficiently from dehydration and has been tested in the formulation of aqueous alumina suspensions. It has been added into slurries stabilized with Tiron®, (HO)2C6H2(SO3Na)2, which permits a high state of dispersion by creating repulsive potential between particles. Trehalose added into such suspensions acts as a lubricant and enhances flowing properties of suspensions because of its strong interaction with water which breaks the hydrogen-bonded network of the solvent. Trehalose addition is beneficial for carrying out shaping methods of alumina components by coagulation as it increases solid concentration in the suspension, which facilitates pouring the suspension into a mould. Unfortunately this addition hinders coagulation of particles. © 2003 Society of Chemical Industry [source] Spectroscopic study of the physical properties making trehalose a stabilizing and shelf life extending compound in food industryQUALITY ASSURANCE & SAFETY OF CROPS & FOOD, Issue 2 2010S. Magazù Abstract Introduction Trehalose, a glass-forming bioprotectant disaccharide, has been demonstrated to possess significant potential within the food industry. It does not interact with reactive molecules such as amino groups from peptides and proteins, preventing the degradation and aggregation due to Maillard reactions. Objective This paper aims to review at the molecular level the effects of trehalose on the structural and dynamical properties of water and on protein to highlight the stabilization and conservation properties on food products. Results and Conclusions The experimental findings presented show that water molecules are arranged in presence of trehalose in a particular configuration which avoids ice formation, so limiting damage due to freezing and cooling. On the other hand, homologous disaccharides, and trehalose to a greater extent, slow down the dynamics of water with a significant influence on the biological activity. These results imply that trehalose has a greater ability to bind volatile substances and deliver superior bioprotective effectiveness. Furthermore trehalose is shown to be incapable of taking part in the denaturation process of lysozyme under thermal stress. [source] Elucidation of the molecular structure of lipid A isolated from both a rough mutant and a wild strain of Aeromonas salmonicida lipopolysaccharides using electrospray ionization quadrupole time-of-flight tandem mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 12 2005Anas El-Aneed The chemical structure of lipid A, isolated by mild acid hydrolysis from a rough mutant and a wild strain of Aeromonas salmonicida lipopolysaccharide, was investigated using electrospray ionization quadrupole time-of-flight (QqToF) hybrid tandem mass spectrometry and showed a great degree of microheterogeneity. The chemical structure of the main constituent of this heterogeneous mixture was identified as a , -D-(1,,,6) linked D-glucosamine disaccharide substituted by two phosphate groups, one being bound to the non-reducing end at position O-4, and the other to the position O-1 of the reducing end of the D-glucosamine disaccharide. The location of the fatty acids linked to the disaccharide backbone was established by identifying diagnostic ions in the conventional QqToF-MS scan. Low-energy collision tandem mass spectrometry analysis of the selected precursor diagnostic ions confirmed, unambiguously, their proposed molecular structures. We have established that myristyloxylauric (C14:0(3- O(12:0))) acid residues were both N-2, and O-3, linked to the non-reducing end of the D-GlcN residue, and that two 3-hydroxymyristic (C14:0(3-OH)) acid chains acylated the remaining positions of the reducing end. The MS and MS/MS data obtained allowed us to determine the complex molecular structure of lipid A. The QqToF-MS/MS instrument has shown excellent superiority over a conventional quadrupole-hexapole-quadrupole tandem instrument which failed to fragment the selected precursor ion. Copyright © 2005 John Wiley & Sons, Ltd. [source] Methyl 2- O -,- l -fucopyranosyl ,- d -glucopyranoside monohydrate: a synchrotron studyACTA CRYSTALLOGRAPHICA SECTION C, Issue 2 2008Magnus Färnbäck The structure of the title compound, C13H24O10·H2O, is stabilized by hydrogen bonds situated adjacent to the glycoside linkage. A direct intramolecular hydrogen bond is present between the fucopyranosyl ring O atom and a glucopyranoside OH group, and a bridging water molecule mediates a hydrogen-bond-based interaction from a fucopyranosyl OH group to the methoxy O atom. The conformation of the disaccharide is described by the glycosidic torsion angles ,H = ,41° and ,H = ,2°. [source] Modulation of activity by Arg407: structure of a fungal ,-1,2-mannosidase in complex with a substrate analogueACTA CRYSTALLOGRAPHICA SECTION D, Issue 3 2008Yuri D. Lobsanov Class I ,-mannosidases (glycoside hydrolase family GH47) play key roles in the maturation of N-glycans and the ER-associated degradation of unfolded glycoproteins. The 1.95,Å resolution structure of a fungal ,-1,2-mannosidase in complex with the substrate analogue methyl-,- d -lyxopyranosyl-(1,,2)-,- d -mannopyranoside (LM) shows the intact disaccharide spanning the ,1/+1 subsites, with the d -lyxoside ring in the ,1 subsite in the 1C4 chair conformation, and provides insight into the mechanism of catalysis. The absence of the C5, hydroxymethyl group on the d -lyxoside moiety results in the side chain of Arg407 adopting two alternative conformations: the minor one interacting with Asp375 and the major one interacting with both the d -lyxoside and the catalytic base Glu409, thus disrupting its function. Chemical modification of Asp375 has previously been shown to inactivate the enzyme. Taken together, the data suggest that Arg407, which belongs to the conserved sequence motif RPExxE, may act to modulate the activity of the enzyme. The proposed mechanism for modulating the activity is potentially a general mechanism for this superfamily. [source] Chondroitin sulphate proteoglycans in the vitreous gel of sheep and goatBIOMEDICAL CHROMATOGRAPHY, Issue 5 2007Spyros S. Skandalis Abstract In the present study, the amounts and the fine structural characteristics of chondroitin sulphate proteoglycans (CSPGs) present in sheep and goat vitreous gels were determined. The results showed that in both examined species hyaluronan was the predominant glycosaminoglycan (GAG), whereas CSPGs were present in minor amounts. CSPGs were identified as versican and collagen IX with versican being the predominant PG type. Fine structural characterization indicated that the CS chains of versican in both mammalian species were of smaller size than those found in collagen IX. The difference in the sulphation pattern of CS chains between versican and collagen IX was also of particular interest. The results indicated that the predominant disaccharide type in CS side chains of versican and collagen IX from both sheep and goat vitreous gels was the 4-sulphated disaccharide. CS chains of versican were found to be richer in 4-sulphated disaccharide units than those in collagen IX, which also contained a significant proportion of non-sulphated disaccharides. These findings showed that, firstly, the CS content and the hydrodynamic size of the CS chain and, secondly, the sulphation pattern of CS chains from versican and collagen IX in both sheep and goat vitreous gels are PG type-dependent. Copyright © 2007 John Wiley & Sons, Ltd. [source] | |||||||||||||||||||||||||||||||||||||||||||