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  Subjects -> CHEMISTRY (Total: 762 journals)
    - ANALYTICAL CHEMISTRY (45 journals)
    - CHEMISTRY (527 journals)
    - CRYSTALLOGRAPHY (22 journals)
    - ELECTROCHEMISTRY (24 journals)
    - INORGANIC CHEMISTRY (40 journals)
    - ORGANIC CHEMISTRY (40 journals)
    - PHYSICAL CHEMISTRY (64 journals)

CHEMISTRY (527 journals)                  1 2 3 4 5 6 | Last

Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement     Hybrid Journal   (30 followers)
ACS Catalysis     Full-text available via subscription   (21 followers)
ACS Chemical Neuroscience     Full-text available via subscription   (10 followers)
ACS Combinatorial Science     Full-text available via subscription   (6 followers)
ACS Macro Letters     Full-text available via subscription   (16 followers)
ACS Medicinal Chemistry Letters     Full-text available via subscription   (16 followers)
ACS Nano     Full-text available via subscription   (158 followers)
ACS Photonics     Full-text available via subscription   (1 follower)
ACS Synthetic Biology     Full-text available via subscription   (7 followers)
Acta Chemica Iasi     Open Access  
Acta Chimica Slovaca     Open Access   (5 followers)
Acta Chromatographica     Full-text available via subscription   (9 followers)
Acta Facultatis Medicae Naissensis     Open Access   (1 follower)
Acta Metallurgica Sinica (English Letters)     Hybrid Journal   (2 followers)
adhäsion KLEBEN & DICHTEN     Hybrid Journal   (1 follower)
Adhesion Adhesives & Sealants     Hybrid Journal   (3 followers)
Adsorption Science & Technology     Full-text available via subscription   (5 followers)
Advanced Functional Materials     Hybrid Journal   (29 followers)
Advances in Chemical Engineering and Science     Open Access   (19 followers)
Advances in Chemical Science     Open Access   (6 followers)
Advances in Colloid and Interface Science     Full-text available via subscription   (12 followers)
Advances in Drug Research     Full-text available via subscription   (13 followers)
Advances in Fluorine Science     Full-text available via subscription   (6 followers)
Advances in Fuel Cells     Full-text available via subscription   (10 followers)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (6 followers)
Advances in Materials Physics and Chemistry     Open Access   (7 followers)
Advances in Nanoparticles     Open Access   (9 followers)
Advances in Organometallic Chemistry     Full-text available via subscription   (7 followers)
Advances in Polymer Science     Hybrid Journal   (35 followers)
Advances in Protein Chemistry     Full-text available via subscription   (4 followers)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (8 followers)
Advances in Quantum Chemistry     Full-text available via subscription   (3 followers)
African Journal of Chemical Education     Open Access  
African Journal of Pure and Applied Chemistry     Open Access  
Afrique Science : Revue Internationale des Sciences et Technologie     Open Access  
Agrokémia és Talajtan     Full-text available via subscription   (2 followers)
Alchemy     Open Access   (2 followers)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (3 followers)
AMB Express     Open Access   (1 follower)
Ambix     Hybrid Journal   (3 followers)
American Journal of Applied Sciences     Open Access   (27 followers)
American Journal of Biochemistry and Biotechnology     Open Access   (80 followers)
American Journal of Biochemistry and Molecular Biology     Open Access   (7 followers)
American Journal of Chemistry     Open Access   (14 followers)
American Journal of Plant Physiology     Open Access   (9 followers)
American Mineralogist     Full-text available via subscription   (2 followers)
Analyst     Full-text available via subscription   (33 followers)
Angewandte Chemie     Hybrid Journal   (12 followers)
Angewandte Chemie International Edition     Hybrid Journal   (143 followers)
Annales UMCS, Chemia     Open Access   (2 followers)
Annual Reports in Computational Chemistry     Full-text available via subscription   (1 follower)
Annual Reports Section A (Inorganic Chemistry)     Full-text available via subscription   (2 followers)
Annual Reports Section B (Organic Chemistry)     Full-text available via subscription   (4 followers)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (8 followers)
Annual Review of Food Science and Technology     Full-text available via subscription   (11 followers)
Anti-Infective Agents     Hybrid Journal   (1 follower)
Applied Organometallic Chemistry     Hybrid Journal   (3 followers)
Applied Spectroscopy     Full-text available via subscription   (11 followers)
Applied Surface Science     Hybrid Journal   (13 followers)
Arabian Journal of Chemistry     Full-text available via subscription   (5 followers)
ARKIVOC     Open Access   (1 follower)
Asian Journal of Biochemistry     Open Access   (1 follower)
Australian Journal of Chemistry     Hybrid Journal   (4 followers)
Autophagy     Full-text available via subscription  
Avances en Quimica     Open Access   (1 follower)
Biocell     Open Access  
Biochemical Pharmacology     Hybrid Journal   (5 followers)
Biochemistry     Full-text available via subscription   (121 followers)
Biochemistry Insights     Open Access   (3 followers)
Biochemistry Research International     Open Access   (3 followers)
BioChip Journal     Hybrid Journal   (1 follower)
Bioinorganic Chemistry and Applications     Open Access   (4 followers)
Biointerface Research in Applied Chemistry     Open Access   (1 follower)
Biointerphases     Open Access  
Biomacromolecules     Full-text available via subscription   (16 followers)
Biomass Conversion and Biorefinery     Partially Free   (5 followers)
Biomedical Chromatography     Hybrid Journal   (7 followers)
Biomolecular NMR Assignments     Hybrid Journal   (2 followers)
BioNanoScience     Partially Free   (4 followers)
Bioorganic & Medicinal Chemistry     Hybrid Journal   (26 followers)
Bioorganic & Medicinal Chemistry Letters     Hybrid Journal   (20 followers)
Bioorganic Chemistry     Hybrid Journal   (5 followers)
Biopolymers     Hybrid Journal   (12 followers)
Biosensors     Open Access   (3 followers)
Biotechnic and Histochemistry     Hybrid Journal   (1 follower)
Boletin de la Sociedad Chilena de Quimica     Open Access  
Bulletin of the Chemical Society of Ethiopia     Open Access   (1 follower)
Bulletin of the Chemical Society of Japan     Full-text available via subscription   (11 followers)
Canadian Association of Radiologists Journal     Full-text available via subscription   (3 followers)
Canadian Journal of Chemistry     Full-text available via subscription   (6 followers)
Canadian Mineralogist     Full-text available via subscription   (1 follower)
Carbohydrate Research     Hybrid Journal   (10 followers)
Carbon     Hybrid Journal   (33 followers)
Catalysis for Sustainable Energy     Open Access   (1 follower)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (3 followers)
Catalysis Science and Technology     Free   (3 followers)
Catalysis Surveys from Asia     Hybrid Journal   (3 followers)
Catalysts     Open Access   (5 followers)
Cellulose     Hybrid Journal   (4 followers)
Central European Journal of Chemistry     Hybrid Journal   (5 followers)

        1 2 3 4 5 6 | Last

Carbohydrate Research    [12 followers]  Follow    
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Print) 0008-6215 - ISSN (Online) 0008-6215
     Published by Elsevier Homepage  [2556 journals]   [SJR: 0.675]   [H-I: 77]
  • Carbohydrate-based Cu(I) stabilizing ligands and their use in the
           synthesis of carbohydrate-ferrocene conjugates
    • Abstract: Publication date: Available online 21 January 2014
      Source:Carbohydrate Research
      Author(s): Magnus S. Schmidt , Kim Leitner , Moritz Welter , Markus Ringwald
      A series of carbohydrate-ferrocene conjugates have been synthesized by copper(I)-catalyzed cycloaddition of carbohydrate-azides and ethynylferrocene (CuAAC). Newly carbohydrate-based tris-triazoles have been used as Cu(I) stabilizing ligands and showed at least comparable, in some cases even better results compared to the use of tris-(benzyltriazolylmethyl)amine (TBTA).
      Graphical abstract image Highlights

      PubDate: 2014-01-24T00:05:41Z
       
  • Glucansucrase acceptor reactions with D-mannose
    • Abstract: Publication date: Available online 23 January 2014
      Source:Carbohydrate Research
      Author(s): Gregory L. Côté , Ryan S. Cormier , Karl E. Vermillion
      The main acceptor product of glucansucrases with D-mannose has not previously been identified. We used glucansucrases that form water-insoluble α-D-glucans to produce increased yields of acceptor products from D-mannose, and identified the major product as 6-O-α-D-glucopyranosyl-D-mannose. Glucansucrases that synthesize insoluble α-D-glucans produced higher yields of the disaccharide compared to typical dextransucrases.
      Graphical abstract image Highlights

      PubDate: 2014-01-24T00:05:41Z
       
  • Efficient desymmetrization of 4,6-di-O-benzyl-myo-inositol by Lipozyme
           TL-IM
    • Abstract: Publication date: 11 March 2014
      Source:Carbohydrate Research, Volume 386
      Author(s): Marcela G. Vasconcelos , Raissa H.C. Briggs , Lucia C.S. Aguiar , Denise M.G. Freire , Alessandro B.C. Simas
      The enantioselective enzymatic desymmetrization of 4,6-di-O-benzyl-myo-inositol, a myo-inositol derivative, was effectively catalyzed by Thermomyces lanuginosus lipase (TL-IM). The product 1D-1-O-acetyl-4,6-di-O-benzyl-myo-inositol, a useful precursor to inositol phosphates, was obtained in excellent yield and enantiomeric excess. Through the investigation of the effects of solvent, biocatalyst load, and temperature, a more economical procedure resulted. The feasibility of biocatalyst reuse was also shown.
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      PubDate: 2014-01-24T00:05:41Z
       
  • New triterpenoid saponins from the aerial parts of Schefflera kwangsiensis
    • Abstract: Publication date: 19 February 2014
      Source:Carbohydrate Research, Volume 385
      Author(s): Ying Wang , Lei Wang , Wen-Jing Wang , Xiao-Qi Zhang , Hai-Yan Tian , Qing-Wen Zhang , Yao-Lan Li , Wen-Cai Ye
      Eight new oleanane-type triterpenoid saponins, named schefflesides A–H (1–8), were isolated from the aerial parts of Schefflera kwangsiensis. The structures of these new compounds were established on the basis of hydrolysis and spectroscopic evidence, including 1D- and 2D-NMR (HSQC, HMBC, ROESY and TOCSY) and HR-MS analyses.
      Graphical abstract image Highlights

      PubDate: 2014-01-24T00:05:41Z
       
  • The reducing end sequence of wheat endosperm cell wall arabinoxylans
    • Abstract: Publication date: 11 March 2014
      Source:Carbohydrate Research, Volume 386
      Author(s): Sunil Ratnayake , Cherie T. Beahan , Damien L. Callahan , Antony Bacic
      Walls from wheat (Triticum aestivum L.) endosperm are composed primarily of hetero-(arabino)xylans (AXs) (70%) and (1→3)(1→4)-β-d-glucans (20%) with minor amounts of cellulose and heteromannans (2% each). To understand the differential solubility properties of the AXs, as well as aspects of their biosynthesis, we are sequencing the xylan backbone and examining the reducing end (RE) sequence(s) of wheat (monocot) AXs. A previous study of grass AXs (switchgrass, rice, Brachypodium, Miscanthus and foxtail millet) concluded that grasses lacked the comparable RE glycosyl sequence (4-β-d-Xylp-(1→4)-β-d-Xylp-(1→3)-α-l-Rhap-(1→2)-α-d-GalpA-(1→4)-d-Xylp) found in dicots and gymnosperms but the actual RE sequence was not determined. Here we report the isolation and structural characterisation of the RE oligosaccharide sequence(s) of wheat endosperm cell wall AXs. Walls were isolated as an alcohol-insoluble residue (AIR) and sequentially extracted with hot water (W-sol Fr) and 1M KOH containing 1% NaBH4 (KOH-sol Fr). Detailed structural analysis of the RE oligosaccharides was performed using a combination of methylation analysis, MALDI-TOF-MS, ESI-QTOF-MS, ESI-MS n and enzymic analysis. Analysis of RE oligosaccharides, both 2AB labelled (from W-sol Fr) and glycosyl-alditol (from KOH-sol Fr), revealed that the RE glycosyl sequence of wheat endosperm AX comprises a linear (1→4)-β-d-Xylp backbone which may be mono-substituted with either an α-l-Araf residue at the reducing end β-d-Xylp residue and/or penultimate RE β-d-Xyl residue; β-d-Xylp-(1→4)-[α-l-Araf-(1→3)](+/−)-β-d-Xylp-(1→4)-[α-l-Araf-(1→3)](+/−)-β-d-Xylp and/or an α-d-GlcpA residue at the reducing end β-d-Xylp residue; β-d-Xylp-(1→4)-[α-l-Araf-(1→3)](+/−)-β-d-Xylp-(1→4)-[α-d-GlcAp-(1→2)]-β-d-Xylp. Thus, wheat endosperm AX backbones lacks the RE sequence found in dicot and gymnosperm xylans; a finding consistent with previous reports from other grass species.
      Graphical abstract image

      PubDate: 2014-01-24T00:05:41Z
       
  • Bacillus thuringiensis: a specific gamma-cyclodextrin producer strain
    • Abstract: Publication date: 11 March 2014
      Source:Carbohydrate Research, Volume 386
      Author(s): Bon Geun Goo , You Jin Hwang , Jae Kweon Park
      An anaerobic microbial isolate Bacillus species, designated B. thuringiensis GU-2, was isolated from soil as a specific γ-cyclodextrin (CD) producer strain in alkaline medium under anaerobic conditions. The optimum pH and temperature for bacterial growth and γ-CD production were estimated to be pH 8.5 and 37°C in the presence of 1.0% starch substrate, respectively. A high purity yield >95% of γ-CD from the total CD yield in the reaction mixture was obtained from starch that was supposed to be converted by gamma-cyclodextrin glycotransferase, tentatively named as γ-CGTase. The maximum γ-CGTase activity was estimated at 2.45U/mL under optimized condition. This is the first report demonstrating the generation of a specific γ-cyclodextrin (CD) producer strain by the action of a γ-CGTase under anaerobic conditions.
      Graphical abstract image

      PubDate: 2014-01-24T00:05:41Z
       
  • Synthesis of bis-cellobiose and bis-glucose derivatives of azacrown
           macrocycles as hosts in complexes with acetylsalicylic acid and
           4-acetamidophenol
    • Abstract: Publication date: 11 March 2014
      Source:Carbohydrate Research, Volume 386
      Author(s): Michalina Pintal , Bogusław Kryczka , Alain Marsura , Stanisław Porwański
      Two new C2 symmetric bis-cellobiose and bis-glucose azacrown derivatives were prepared according to the one-step procedure using azacrown ethers and azidosaccharides. Their complexes with aspirin and paracetamol were studied with the use of proton NMR spectroscopy. It was found that these pseudocryptands bind aspirin and paracetamol but each one in a different manner.
      Graphical abstract image

      PubDate: 2014-01-24T00:05:41Z
       
  • Oxidation of sialic acid using hydrogen peroxide as a new method to tune
           the reducing activity
    • Abstract: Publication date: Available online 14 January 2014
      Source:Carbohydrate Research
      Author(s): C. Neyra , J. Paladino , M. Le Borgne
      Functionalized sialic acids are useful intermediates to prepare a wide range of biological products. As they often occur at a non-reducing terminal of oligosaccharides, the most used technique to activate them is by periodate-mediated oxidation of their glycerol side chain. Here, we describe an alternative, non toxic and environmentally-friendly method to activate the sialic acid residues by hydrogen peroxide oxidation. Four oxidative systems involving H2O2, EDTA, iron chloride and UV light were studied and the products obtained were analyzed by LC-MS and NMR, before and after a derivatization reaction. At first, we observed, for each system, an irreversible decarbonylation reaction at the reducing end. Then, the decarbonylated sialic acid (DSA) was oxidized and fragmented into a mix of carbonyls and carboxyl acids, more or less fast according to the experimental conditions. Analysis of the reaction indicated an apparent radical mechanism and heterolytic alpha-hydroxy-hydroperoxide cleavages. The modest reducing activity was mainly explained as a consequence of over-oxidation reactions.
      Graphical abstract image Highlights

      PubDate: 2014-01-16T00:06:39Z
       
  • Designing of a novel dextransucrase efficient in acceptor reactions
    • Abstract: Publication date: Available online 14 January 2014
      Source:Carbohydrate Research
      Author(s): Mahmut Parlak , Duran Ustek , Aziz Tanriseven
      Dextransucrase is produced by Leuconostoc, Streptococcus and Lactobacillus Species. The enzyme synthesizes dextran and acceptor products some of which act as prebiotics that are increasingly used in such industries as food, medicine, and cosmetics. B-512 F Leuconostoc mesenteroides dextransucrase (DSR-S) is the preferred enzyme in commercial production of dextran and prebiotics. In the present work, a novel dextransucrase which is efficient in prebiotics production was designed. The enzyme was produced at optimal conditions in E. coli by truncation and fusion to glutathione S-transferase (GST) in the gene from Leuconostoc mesenteroides B-512 FMC. The novel enzyme (MW: 119 kDa) was active and carried out dextran biosynthesis and acceptor reactions effectively. The novel dextransucrase (fTDSR-S) was produced by truncating signal, variable, and the glucan-binding regions in the gene and fusion of gst gene at the 5’ end. fTDSR-S was characterized in detail and compared to the DSR-S. Truncation and fusion resulted in an increase in fTDSR-S biosynthesis in E. coli BL21 (DE3) by 35 fold. fTDSR-S leads to production of dextran as well as increased acceptor reactions. Due to GST fusion, it was possible to immobilize fTDSR-S covalently onto Eupergit C successfully. It was also found that the size of the active site of dextransucrase is 49 amino acids shorter than that reported previously in the literature.
      Graphical abstract image Highlights

      PubDate: 2014-01-16T00:06:39Z
       
  • Structure and gene cluster of the O-antigen of Escherichia coli O36
    • Abstract: Publication date: Available online 14 January 2014
      Source:Carbohydrate Research
      Author(s): Andrei V. Perepelov , Quan Wang , Evgeniya A. Levina , Olga G. Ovchinnikova , Ye Qian , Alexander S. Shashkov , Lei Wang , Yuriy A. Knirel
      The O-polysaccharide (O-antigen) of Escherichia coli O36 was isolated from the lipopolysaccharide and studied by sugar analyses and Smith degradation along with 1H and 13C NMR spectroscopy. The following structure of the branched pentasaccharide repeating unit was established, which is unique among the known structures of bacterial polysaccharides: The O-antigen gene cluster of E. coli O36 has been sequenced. The gene functions were tentatively assigned by comparison with sequences in the available databases and found to be in full agreement with the O-polysaccharide structure.
      Graphical abstract image

      PubDate: 2014-01-16T00:06:39Z
       
  • Importance of altered glycoprotein-bound N- and O-glycans for
           epithelial-to-mesenchymal transition and adhesion of cancer cells
    • Abstract: Publication date: Available online 15 January 2014
      Source:Carbohydrate Research
      Author(s): Tobias Lange , Timur R. Samatov , Alexander G. Tonevitsky , Udo Schumacher
      Aberrant glycosylation of cell surface glycoproteins acquired during malignant progression is a common characteristic of human cancer cells. Several biological processes and molecular mechanisms relevant for tumour progression are accompanied by altered mRNA expression levels of certain glycosyltransferases resulting in unusual ratios of common glycoconjugates presented in a cancer cell’s glycocalyx or even in the development of unusual, cancer-characterizing carbohydrates. This mini-review aims to give a concise overview on the current knowledge of the functional relevance of altered O- and N-glycans during two critical steps of tumour progression: (I) epithelial-to-mesenchymal transition of primary tumour cells during intravasation and (II) adhesion of circulating tumour cells towards the vascular wall during extravasation at a distant metastatic site. Characteristic lectin binding patterns reflecting these glycosylation changes and the resulting prognostic impact of certain lectin binding sites in different neoplasias are reviewed as well.
      Graphical abstract image Highlights

      PubDate: 2014-01-16T00:06:39Z
       
  • Synthesis and biological evaluation of arabinose 5-phosphate mimics
           modified at position five
    • Abstract: Publication date: Available online 15 January 2014
      Source:Carbohydrate Research
      Author(s): Laura Cipolla , Cristina Airoldi , Paola Sperandeo , Serena Gianera , Alessandra Polissi , Francesco Nicotra , Luca Gabrielli
      A set of new metabolically stable arabinose 5-phosphate analogues possessing phosphate mimetic groups at position 5 was synthesised. Their ability to interact with arabinose 5-phosphate isomerase from Pseudomonas aeruginosa was evaluated by STD-NMR studies. The synthesised compounds were also characterised for their activity in vivo on P. aeruginosa and E. coli strains. Unfortunately, none of the synthesised compounds was able neither to bind API nor to inhibit bacterial growth.
      Graphical abstract image

      PubDate: 2014-01-16T00:06:39Z
       
  • Structural and genetic studies of the O-antigen of Enterobacter cloacae
           G2277
    • Abstract: Publication date: Available online 14 January 2014
      Source:Carbohydrate Research
      Author(s): Andrei V. Perepelov , Min Wang , Andrei V. Filatov , Xi Guo , Alexander S. Shashkov , Lei Wang , Yuriy A. Knirel
      The O-polysaccharide was isolated by mild acid degradation of the lipopolysaccharide of Enterobacter cloacae G2277 and studied by sugar analysis along with 1D and 2D 1H and 13C NMR spectroscopy. The following structure of the linear pentasaccharide repeating unit was established, where a galacturonic acid (GalA) residue is mono-O-acetylated at position either 2 or 3: The O-antigen gene cluster of E. cloacae G2277 was sequenced. The gene functions were tentatively assigned by comparison with sequences in the available databases and found to be in agreement with the O-polysaccharide structure.
      Graphical abstract image Highlights

      PubDate: 2014-01-16T00:06:39Z
       
  • Mechanism of 1-(1-propylsulfonic)-3-methylimidazolium chloride catalyzed
           transformation of D-glucose to 5-hydroxymethylfurfural in DMSO: an NMR
           study
    • Abstract: Publication date: Available online 15 January 2014
      Source:Carbohydrate Research
      Author(s): Ananda S. Amarasekara , Ashfaqur Razzaq
      The conversion of D-glucose to 5-hydroxymethylfurfural (HMF) in the presence of 5.48 mol% 1-(1-propylsulfonic)-3-methylimidazolium chloride acidic ionic liquid catalyst in DMSO at 150 °C was studied using 1H, 13C NMR and visible spectroscopy. The HMF yield rapidly increases in the first 100 minutes of reaction, however yield drops beyond 100 minutes and levels off to a maximum yield of about 15.7% around 600 minutes. The visible spectroscopy study of the reaction mixture suggests that rate of HMF formation slows down after 100 minutes due to increase in the rate of humin formation after first 100 minutes. A mechanism has been proposed and key intermediates in the pathway could be identified by studying the 13C NMR spectra of acidic ionic liquid catalyzed transformations of C-1 and C-2 13C labeled D-glucose under identical conditions. The proposed mechanism involves the isomerization of D-glucose to D-fructose via the complexation of the open chain sugar with the imidazolium cation of the acidic ionic liquid catalyst.
      Graphical abstract image Highlights

      PubDate: 2014-01-16T00:06:39Z
       
  • From D-glucuronic acid to L-iduronic acid derivatives via a radical tandem
           decarboxylation-cyclization
    • Abstract: Publication date: Available online 15 January 2014
      Source:Carbohydrate Research
      Author(s): Stéphane Salamone , Michel Boisbrun , Claude Didierjean , Yves Chapleur
      A synthesis to L-iduronic derivatives, major components of heparin derived pentasaccharides was accomplished by formal inversion of configuration at C-5 of a D-glucuronic acid derivative through radical formation at C-5 using Barton decarboxylation followed by intramolecular radical addition on an acetylenic tether at O-4 giving exclusively a bicylic sugar of L-ido configuration. Oxidation and ring opening of this bicyclic sugar led to a L-iduronate. This method opens the way to short syntheses of pentasaccharidic moiety of Idraparinux and congeners.
      Graphical abstract image Highlights

      PubDate: 2014-01-16T00:06:39Z
       
  • Bacterial expression and functional reconstitution of human heparanase
    • Abstract: Publication date: Available online 14 January 2014
      Source:Carbohydrate Research
      Author(s): Sophie Winkler , Daniela Schweiger , Zheng Wei , Erich Rajkovic , Andreas J. Kungl
      Human heparanase is a heparan sulfate degrading enzyme located in the extracellular matrix playing a decisive role in angiogenesis and tumour metastasis. Translated as a 65kDa inactive prae-form, the protein is processed into an 8kDa and a 50kDa subunit which form a non-covalently associated active heterodimer. We have expressed the two subunits separately in E.coli which yielded active human heparanase upon reconstitution. The two purified subunits folded independently and secondary structure analysis by far-UV CD spectroscopy gave 33.1/11.1% α/ß content for the 50kDa subunit and 6.9/49% α/ß content for the 8kDa subunit. This heparanase expression system is easy and can be used for efficient screening for enzyme inhibitors.
      Graphical abstract image

      PubDate: 2014-01-16T00:06:39Z
       
  • Graphical contents list
    • Abstract: Publication date: 30 January 2014
      Source:Carbohydrate Research, Volume 384




      PubDate: 2014-01-12T00:05:37Z
       
  • Formation of degradation compounds from lignocellulosic biomass in the
           biorefinery: sugar reaction mechanisms
    • Abstract: Publication date: 19 February 2014
      Source:Carbohydrate Research, Volume 385
      Author(s): Helena Rasmussen , Hanne R. Sørensen , Anne S. Meyer
      The degradation compounds formed during pretreatment when lignocellulosic biomass is processed to ethanol or other biorefinery products include furans, phenolics, organic acids, as well as mono- and oligomeric pentoses and hexoses. Depending on the reaction conditions glucose can be converted to 5-(hydroxymethyl)-2-furaldehyde (HMF) and/or levulinic acid, formic acid and different phenolics at elevated temperatures. Correspondingly, xylose can follow different reaction mechanisms resulting in the formation of furan-2-carbaldehyde (furfural) and/or various C-1 and C-4 compounds. At least four routes for the formation of HMF from glucose and three routes for furfural formation from xylose are possible. In addition, new findings show that biomass monosaccharides themselves can react further to form pseudo-lignin and humins as well as a wide array of other compounds when exposed to high temperatures. Hence, several aldehydes and ketones and many different organic acids and aromatic compounds may be generated during hydrothermal treatment of lignocellulosic biomass. The reaction mechanisms are of interest because the very same compounds that are possible inhibitors for biomass processing enzymes and microorganisms may be valuable biobased chemicals. Hence a new potential for industrial scale synthesis of chemicals has emerged. A better understanding of the reaction mechanisms and the impact of the reaction conditions on the product formation is thus a prerequisite for designing better biomass processing strategies and forms an important basis for the development of new biorefinery products from lignocellulosic biomass as well.
      Graphical abstract image

      PubDate: 2014-01-12T00:05:37Z
       
  • Editorial board
    • Abstract: Publication date: 30 January 2014
      Source:Carbohydrate Research, Volume 384




      PubDate: 2014-01-12T00:05:37Z
       
  • Novel substrates for the measurement of endo-1,4-β-glucanase
           (endo-cellulase)
    • Abstract: Publication date: 19 February 2014
      Source:Carbohydrate Research, Volume 385
      Author(s): Barry V. McCleary , David Mangan , Robin Daly , Sébastien Fort , Ruth Ivory , Niall McCormack
      A specific and sensitive substrate for the assay of endo-1,4-β-glucanase (cellulase) has been prepared. The substrate mixture comprises benzylidene end-blocked 2-chloro-4-nitrophenyl-β-cellotrioside (BzCNPG3) in the presence of thermostable β-glucosidase. Hydrolysis by exo-acting enzymes such as β-glucosidase and exo-β-glucanase is prevented by the presence of the benzylidene group on the non-reducing end d-glucosyl residue. On hydrolysis by cellulase, the 2-chloro-4-nitrophenyl-β-glycoside is immediately hydrolysed to 2-chloro-4-nitrophenol and free d-glucose by the β-glucosidase in the substrate mixture. The reaction is terminated and colour developed by the addition of a weak alkaline solution. The assay procedure is simple to use, specific, accurate, robust and readily adapted to automation. This procedure should find widespread applications in biomass enzymology and in the specific assay of endo-1,4-β-glucanase in general.
      Graphical abstract image

      PubDate: 2014-01-08T00:05:44Z
       
  • Recent developments in glycosyl urea synthesis
    • Abstract: Publication date: 19 February 2014
      Source:Carbohydrate Research, Volume 385
      Author(s): Matthew J. McKay , Hien M. Nguyen
      The area of sugar urea derivatives has received considerable attention in recent years because of the unique structural properties and activities that these compounds display. The urea-linkage at the anomeric center is a robust alternative to the naturally occurring O- and N-glycosidic linkages of oligosaccharides and glycoconjugates, and the natural products that have been identified to contain these structures show remarkable biological activity. While methods for installing the β-urea-linkage at the anomeric center have been around for decades, the first synthesis of α-urea glycosides has been much more recent. In either case, the selective synthesis of glycosyl ureas can be quite challenging, and a mixture of α- and β-isomers will often result. This paper will provide a comprehensive review of the synthetic approaches to α- and β-urea glycosides and examine the structure and activity of the natural products and their analogues that have been identified to contain them.
      Graphical abstract image Highlights

      PubDate: 2014-01-08T00:05:44Z
       
  • The structure and immunomodulatory activity on intestinal epithelial cells
           of the EPSs isolated from Lactobacillus helveticus sp. Rosyjski and
           Lactobacillus acidophilus sp. 5e2
    • Abstract: Publication date: 30 January 2014
      Source:Carbohydrate Research, Volume 384
      Author(s): Daniel A. Patten , Shaun Leivers , Marcus J. Chadha , Mohammed Maqsood , Paul N. Humphreys , Andrew P. Laws , Andrew Collett
      The Lactic acid bacteria (LAB) Lactobacillus acidophilus sp. 5e2 and Lactobacillus helveticus sp. Rosyjski both secrete exopolysaccharides (EPSs) into their surrounding environments during growth. A number of EPSs have previously been shown to exhibit immunomodulatory activity with professional immune cells, such as macrophages, but only limited studies have been reported of their interaction with intestinal epithelial cells. An investigation of the immunomodulatory potential of pure EPSs, isolated from cultures of Lactobacillus acidophilus sp. 5e2 and Lactobacillus helveticus sp. Rosyjski, with the HT29-19A intestinal epithelial cell line are reported here. For the first time the structure of the EPS from Lactobacillus helveticus sp. Rosyjski which is a hetropolysaccharide with a branched pentasaccharide repeat unit containing d-glucose, d-galactose and N-acetyl-d-mannosamine is described. In response to exposure to lactobacilli EPSs HT29-19A cells produce significantly increased levels of the proinflammatory cytokine IL-8. Additionally, the EPSs differentially modulate the mRNA expression of Toll-like receptors. Finally, the pre-treatment of HT29-19A cells with the EPSs sensitises the cells to subsequent challenge with bacterial antigens. The results reported here suggest that EPSs could potentially play a role in intestinal homeostasis via a specific interaction with intestinal epithelial cells.
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      PubDate: 2014-01-08T00:05:44Z
       
  • Structural analysis of O-polysaccharide chains extracted from different
           Salmonella Typhimurium strains
    • Abstract: Publication date: 19 February 2014
      Source:Carbohydrate Research, Volume 385
      Author(s): Francesca Micoli , Neil Ravenscroft , Paola Cescutti , Giuseppe Stefanetti , Silvia Londero , Simona Rondini , Calman A. MacLennan
      Salmonella Typhimurium is the major cause of invasive nontyphoidal Salmonella disease in Africa, with high mortality among children and HIV-infected individuals. Currently, no vaccine is available for use in humans. Antibodies directed against the O-polysaccharide of the lipopolysaccharide molecule of Salmonella mediate bacterial killing and are protective, and conjugation of the O-polysaccharide to a carrier protein represents a possible strategy for vaccine development. Here we have purified the O-polysaccharide from six different strains of S. Typhimurium and fully characterized them using analytical methods including HPLC–SEC, HPAEC-PAD, GC, GC–MS, 1D and 2D NMR spectroscopy. All the O-polysaccharide samples showed a similar bimodal molecular mass distribution, but differed with respect to the amount and position of O-acetylation and glucosylation. For some strains, O-acetyl groups were found not only on C-2 of abequose (factor 5 specificity), but also on C-2 and C-3 of rhamnose; glucose was found to be linked 1→4 or 1→6 to galactose in different amounts according to the strain of origin. This structural variability could have an impact on the immunogenicity of corresponding glycoconjugate vaccines and different strains need to be evaluated in order to identify the appropriate source of O-polysaccharide to use for the development of a candidate conjugate vaccine with broad coverage against S. Typhimurium.
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      PubDate: 2014-01-04T00:05:54Z
       
  • Solid-state 13C NMR study of the mobility of polysaccharides in the cell
           walls of two apple cultivars of different firmness
    • Abstract: Publication date: Available online 3 January 2014
      Source:Carbohydrate Research
      Author(s): Jovyn K.T. Ng , Zoran D. Zujovic , Bronwen G. Smith , Jason W. Johnston , Roswitha Schröder , Laurence D. Melton
      Solid-state 13C nuclear magnetic resonance (NMR) was used to compare differences in mobility of the cell wall polysaccharides of ‘Scifresh’ and ‘Royal Gala’ apples after 20 weeks of storage. The texture of ‘Scifresh’ apples was markedly firmer than that of ‘Royal Gala’ at the end of storage. In a novel approach Two Pulse Phase Modulation (TPPM) decoupling was combined with cross polarisation (CP) and single pulse excitation (SPE) experiments. The resulting high resolution solid-state SPE spectra, unprecedented for apple cell walls, allowed a detailed insight into the physical and chemical properties of very mobile polysaccharides such as the arabinan and galactan side chains of the pectic polysaccharide rhamnogalacturonan I (RG-I). NMR showed that the cellulose rigidity was the same in the two cultivars, while arabinans were more mobile than galactans in both. Unexpectedly, arabinans in ‘Scifresh’ cell walls were more mobile than those in ‘Royal Gala’ which was unforeseen considering the greater firmness of the ‘Scifresh’ cultivar.
      Graphical abstract image Highlights

      PubDate: 2014-01-04T00:05:54Z
       
  • Five natural carbohydrates from the leaves of Sauropus rostratus
    • Abstract: Publication date: 30 January 2014
      Source:Carbohydrate Research, Volume 384
      Author(s): Chunhua Wang , Wen Li , Hongli Liu , Juan Wang , Guoqiang Li , Guocai Wang , Yaolan Li
      Three new hexose derivatives (1–3), together with two known ones (4,5), were isolated from the leaves of Sauropus rostratus. The structures of new compounds were elucidated on the basis of the spectroscopic methods including 1D and 2D NMR (HSQC, 1H–1H COSY, HMBC and NOESY) and HR-MS analyses. The absolute configurations of three new compounds were established by the modified Mosher’s method.
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      PubDate: 2013-12-27T09:03:08Z
       
  • Exploring the binding of 4-thiothymidine with human serum albumin by
           spectroscopy, atomic force microscopy, and molecular modeling methods
    • Abstract: Publication date: 30 January 2014
      Source:Carbohydrate Research, Volume 384
      Author(s): Juling Zhang , Huaimin Gu , Xiaohui Zhang
      The interaction of 4-thiothymidine (S4TdR) with human serum albumin (HSA) was studied by equilibrium dialysis under normal physiological conditions. In this work, the mechanism of the interaction between S4TdR and human serum albumin (HSA) was exploited by fluorescence, UV, CD circular, and SERS spectroscopic. Fluorescence and UV spectroscopy suggest that HSA intensities are significantly decreased when adding S4TdR to HAS, and the quenching mechanism of the fluorescence is static. Also, the ΔG, ΔH, and ΔS values across temperature indicated that hydrophobic interaction was the predominant binding force. The CD circular results show that there is little change in the secondary structure of HSA except the environment of amino acid changes when adding S4TdR to HSA. The surface-enhanced Raman scattering (SERS) shows that the interaction between S4TdR and HSA can be achieved through different binding sites which are probably located in the II A and III A hydrophobic pockets of HSA which correspond to Sudlow’s I and II binding sites. In addition, the molecular modeling displays that S4TdR–HSA complex is stabilized by hydrophobic forces, which result from amino acid residues. The atomic force microscopy results revealed that the single HSA molecular dimensions were larger after interaction of 4-thiothymidine. This work would be useful to understand the state of the transportation, distribution, and metabolism of the anticancer drugs in the human body, and it could provide a useful biochemistry parameter for the development of new anti-cancer drugs and research of pharmacology mechanisms.
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      PubDate: 2013-12-27T09:03:08Z
       
  • Spectroscopic investigation of new water soluble MnII2 and MgII2 complexes
           for the substrate binding models of xylose/glucose isomerases
    • Abstract: Publication date: 30 January 2014
      Source:Carbohydrate Research, Volume 384
      Author(s): Ayan Patra , Manindranath Bera
      In methanol, the reaction of stoichiometric amounts of Mn(OAc)2·4H2O and the ligand H3hpnbpda [H3hpnbpda= N,N′-bis(2-pyridylmethyl)-2-hydroxy-1,3-propanediamine-N,N′-diacetic acid] in the presence of NaOH, afforded a new water soluble dinuclear manganese(II) complex, [Mn2(hpnbpda)(μ-OAc)] (1). Similarly, the reaction of Mg(OAc)2·4H2O and the ligand H3hpnbpda in the presence of NaOH, in methanol, yielded a new water soluble dinuclear magnesium(II) complex, [Mg2(hpnbpda)(μ-OAc)(H2O)2] (2). DFT calculations have been performed for the structural optimization of complexes 1 and 2. The DFT optimized structure of complex 1 shows that two manganese(II) centers are in a distorted square pyramidal geometry, whereas the DFT optimized structure of complex 2 reveals that two magnesium(II) centers adopt a six-coordinate distorted octahedral geometry. To understand the mode of substrate binding and the mechanistic details of the active site metals in xylose/glucose isomerases (XGI), we have investigated the binding interactions of biologically important monosaccharides d-glucose and d-xylose with complexes 1 and 2, in aqueous alkaline solution by a combined approach of FTIR, UV–vis, fluorescence, and 13C NMR spectroscopic techniques. Fluorescence spectra show the binding-induced gradual decrease in emission of complexes 1 and 2 accompanied by a significant blue shift upon increasing the concentration of sugar substrates. The binding modes of d-glucose and d-xylose with complex 2 are indicated by their characteristic coordination induced shift (CIS) values in 13C NMR spectra for C1 and C2 carbon atoms.
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      PubDate: 2013-12-27T09:03:08Z
       
  • Synthesis of the NAG–NAM disaccharide via a versatile intermediate
    • Abstract: Publication date: 30 January 2014
      Source:Carbohydrate Research, Volume 384
      Author(s): Ramu Enugala , Marina J.D. Pires , M. Manuel B. Marques
      A simple strategy for the synthesis of a β-GlcNAc-(1→4)-MurNAc (NAG–NAM) moiety, crucial for the preparation of synthetic components of a bacterial peptidoglycan, was achieved. This strategy relies on the use of three O-protecting groups, 4,6-O-benzilidene acetal, benzyl, and acetyl group, which allows further regioselective manipulation at O-3, O-4 positions, and on the insertion of the peptide chain at the lactate moiety in an advanced and versatile intermediate. Overall, a simple route to achieve the biological relevant NAG–NAM is presented, which may serve as a conceptual framework in the designing of synthetic strategies of different natural and non-natural polysaccharides.
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      PubDate: 2013-12-27T09:03:08Z
       
  • Is an acyl group at O-3 in glucosyl donors able to control
           α-stereoselectivity of glycosylation? The role of conformational
           mobility and the protecting group at O-6
    • Abstract: Publication date: 30 January 2014
      Source:Carbohydrate Research, Volume 384
      Author(s): Bozhena S. Komarova , Maria V. Orekhova , Yury E. Tsvetkov , Nikolay E. Nifantiev
      The stereodirecting effect of a 3-O-acetyl protecting group, which is potentially capable of the remote anchimeric participation, and other protecting groups in 2-O-benzyl glucosyl donors with flexible and rigid conformations has been investigated. To this aim, an array of N-phenyltrifluoroacetimidoyl and sulfoxide donors bearing either 3-O-acetyl or 3-O-benzyl groups in combination with 4,6-di-O-benzyl, 6-O-acyl-4-O-benzyl, or 4,6-O-benzylidene protecting groups was prepared. The conformationally flexible 3-O-acetylated glucosyl donor protected at other positions with O-benzyl groups demonstrated very low or no α-stereoselectivity upon glycosylation of primary or secondary acceptors. On the contrary, 3,6-di-O-acylated glucosyl donors proved to be highly α-stereoselective as well as the donor having a single potentially participating acetyl group at O-6. The 3,6-di-O-acylated donor was shown to be the best α-glucosylating block for the primary acceptor, whereas the best α-selectivity of glycosylation of the secondary acceptor was achieved with the 6-O-acylated donor. Glycosylation of the secondary acceptor with the conformationally constrained 3-O-acetyl-4,6-O-benzylidene-protected donor displayed under standard conditions (−35°C) even lower α-selectivity as compared to the 3-O-benzyl analogue. However, increasing the reaction temperature essentially raised the α-stereoselectivities of glycosylation with both 3-O-acetyl and 3-O-benzyl donors and made them almost equal. The stereodirecting effects of protecting groups observed for N-phenyltrifluoroacetimidoyl donors were also generally proven for sulfoxide donors.
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      PubDate: 2013-12-23T00:05:43Z
       
  • Editorial board
    • Abstract: Publication date: 13 January 2014
      Source:Carbohydrate Research, Volume 383




      PubDate: 2013-12-23T00:05:43Z
       
  • Graphical contents list
    • Abstract: Publication date: 13 January 2014
      Source:Carbohydrate Research, Volume 383




      PubDate: 2013-12-23T00:05:43Z
       
  • Depolymerization of sulfated polysaccharides under hydrothermal conditions
    • Abstract: Publication date: 30 January 2014
      Source:Carbohydrate Research, Volume 384
      Author(s): Minoru Morimoto , Masaki Takatori , Tetsuya Hayashi , Daiki Mori , Osamu Takashima , Shinichi Yoshida , Kimihiko Sato , Hitoshi Kawamoto , Jun-ichi Tamura , Hironori Izawa , Shinsuke Ifuku , Hiroyuki Saimoto
      Fucoidan and chondroitin sulfate, which are well known sulfated polysaccharides, were depolymerized under hydrothermal conditions (120–180°C, 5–60min) as a method for the preparation of sulfated polysaccharides with controlled molecular weights. Fucoidan was easily depolymerized, and the change of the molecular weight values depended on the reaction temperature and time. The degree of sulfation and IR spectra of the depolymerized fucoidan did not change compared with those of untreated fucoidan at reaction temperatures below 140°C. However, fucoidan was partially degraded during depolymerization above 160°C. Nearly the same depolymerization was observed for chondroitin sulfate. These results indicate that hydrothermal treatment is applicable for the depolymerization of sulfated polysaccharides, and that low molecular weight products without desulfation and deformation of the initial glycan structures can be obtained under mild hydrothermal conditions.
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      PubDate: 2013-12-23T00:05:43Z
       
  • Characterization of laminaran and a highly sulfated polysaccharide from
           Sargassum fusiforme
    • Abstract: Publication date: Available online 18 December 2013
      Source:Carbohydrate Research
      Author(s): Weihua Jin , Wenjing Zhang , Jing Wang , Sumei Ren , Ni Song , Delin Duan , Quanbin Zhang
      The crude polysaccharide (HFS) from Sargassum fusiforme (Hizikia fusiforme) was extracted using 0.1 M HCl and was fractionated by anion-exchange chromatography into three fractions: HFS-1, HFS-2, and HFS-3. Based on the chemical analysis, HFS-1 was composed of laminaran, HFS-2 was a mixture of alginate and sulfated heteropolysaccharides, and HFS-3 was primarily composed of sulfated galactofucan. The NMR spectra revealed that HFS-1 was composed of a soluble laminaran with chains that are terminated by β-D-glucose residues. In contrast, the spectra obtained for HFS-2 was still complex, even after most of the alginate was removed. In addition, HFS-3 might contain 3-linked fucan sulfated at C-2, 6-linked galactan sulfated at C-2 and branched at C-4 by 2-sulfated Fuc, and galactofucan with a backbone of either alternating Gal and Fuc sulfated at C-2 or alternating (Gal)n and (Fuc)n sulfated at C-2. Moreover, HFS-3 also contained small amounts of fucoglucuronomannan and xylan.
      Graphical abstract image Highlights

      PubDate: 2013-12-19T00:05:51Z
       
  • Fructose compared with glucose is more a potent glycoxidation agent in
           vitro, but not under carbohydrate-induced stress in vivo: potential role
           of antioxidant and antiglycation enzymes
    • Abstract: Publication date: 30 January 2014
      Source:Carbohydrate Research, Volume 384
      Author(s): Halyna M. Semchyshyn , Jacek Miedzobrodzki , Maria M. Bayliak , Liudmyla M. Lozinska , Bohdana V. Homza
      The contribution of carbohydrates to non-enzymatic processes such as glycation/autoxidation has been extensively investigated over the last decades. This may be attributed to either beneficial or detrimental effects of reducing carbohydrates, and most studies in the field of glycoxidation are focused on glucose. Non-enzymatic reactions of fructose have not been as thoroughly investigated as those of glucose. To compare glucose and fructose involvement in the generation of glycoxidation products under experimental conditions close to the physiological situation, we used intact Saccharomyces cerevisiae cells as in vivo model and cell-free extracts prepared from whole yeast cells as in vitro model. Both intact cells and cell-free extracts were incubated with glucose or fructose. It was shown that: (i) in vitro fructose was more reactive than glucose and produced higher level of autoxidation and glycation products; (ii) no substantive differences were observed for the effect of glucose and fructose on the intracellular level of glycoxidation products, when intact yeast cells were exposed to the high concentration of hexoses; (iii) the activity of defensive enzymes (superoxide dismutase, catalase, glyoxalases, and glutathione reductase) was increased in both glucose- and fructose-stressed yeasts, indicating the development of oxidative/carbonyl stress; (iv) glucose-6-phosphate dehydrogenase activity significantly dropped in yeast exposed to both hexoses, demonstrating its high sensitivity to reactive oxygen and carbonyl species; and (v) fructose more markedly activated glyoxalases than glucose. Involvement of glucose and fructose in the glycoxidation reactions as well as potential role of antioxidant and antiglycation enzymes in yeast protection against glycoxidation are discussed.
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      PubDate: 2013-12-19T00:05:51Z
       
  • Synthesis of two trisaccharides related to the hepatoprotective
           phenylethanoids leonoside E and F isolated from Leonurus japonicus Houtt
    • Abstract: Publication date: 30 January 2014
      Source:Carbohydrate Research, Volume 384
      Author(s): Darshita Budhadev , Balaram Mukhopadhyay
      The chemical synthesis of two trisaccharides related to leonoside E and F is reported. The target oligosaccharides were prepared in the form of their p-methoxyphenyl glycosides using a common disaccharide acceptor. All reaction steps were high yielding (>80%) and the stereoselective glycosylations were achieved by activation of the thioglycoside donors using N-iodosuccinimide in the presence of La(OTf)3.
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      PubDate: 2013-12-15T12:02:16Z
       
  • Conformational studies of gas-phase ribose and 2-deoxyribose by density
           functional, second order PT and multi-level method calculations: the
           pyranoses, furanoses, and open-chain structures
    • Abstract: Publication date: 30 January 2014
      Source:Carbohydrate Research, Volume 384
      Author(s): Marek Szczepaniak , Jerzy Moc
      We present an extensive computational study of a complex conformational isomerism of two gas phase pentoses of biological and potential astrobiological importance, d-ribose and 2-deoxy-d-ribose. Both cyclic (α- and β-pyranoses, α- and β-furanoses) and open-chain isomers have been probed using second order Møller–Plesset perturbation theory (MP2), M06-2X density functional, and multi-level G4 methods. This study revealed a multitude of existing minima structures. Numerous furanose conformers found are described with the Altona and Sundaralingam pseudorotation parameters. In agreement with the recent gas-phase microwave (MW) investigation of Cocinero et al., the calculated free ribose isomers of lowest energy are the two β-pyranoses with the 1C4 and 4C1 ring chair conformations. Both β-pyranoses lie within 0.9kJ/mol in terms of ΔG(298K) (G4), thus challenge the computational methods used to predict the ribose global minimum. The calculated most favoured ribofuranose is the α-anomer having the twist 2T1 ring conformation, put 10.4kJ/mol higher in ΔG than the global minimum. By contrast with d-ribose, the lowest energy 2-deoxy-d-ribose is the α-pyranose, with the most stable 2-deoxy-d-furanose (the α-anomer) being only 6.2kJ/mol higher in free energy. For both pentoses, the most favoured open-chain isomers are significantly higher in energy than the low-lying cyclic forms. A good overall agreement is observed between the M06-2X and MP2 results in terms of both the existing low-energy minima structures and intramolecular H-bonding geometrical parameters. The natural orbital analysis confirms the occuring of the endo- and exo-anomeric effects and maximization of intramolecular H-bonding in the lowest-lying pyranoses and furanoses of both sugars.
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      PubDate: 2013-12-15T12:02:16Z
       
  • Characterization and mechanism of action of Microbacterium imperiale
           glucan 1,4-α-maltotriohydrolase
    • Abstract: Publication date: Available online 1 December 2013
      Source:Carbohydrate Research
      Author(s): Chunsen Wu , Xing Zhou , Yan Xu , Hongyan Li , Yaoqi Tian , Xueming Xu , Zhengyu Jin
      In this study, glucan 1,4-α-maltotriohydrolase (AMTS) from Microbacterium imperiale was purified and characterized. Hydrolysis by AMTS was affected by starch structure (e.g., amylose versus amylopectin) and hydrolysis time. During the initial phase of hydrolysis of maltooligosaccharides (G4–G7), AMTS displayed a unique transfer specificity to the transfer of maltotriosyl units. After extensive hydrolysis, maltotriose became the major end product, followed by glucose and maltose. Maltotetraose (G4) was the smallest donor in transglycosylation reactions by AMTS. This is the first study that reports transglycosylation activity of AMTS on maltooligosaccharides. The results of this study suggest that high purity maltotriose can be produced by the hydrolytic action of AMTS on starch.
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      PubDate: 2013-12-03T00:05:56Z
       
  • Synthesis and conformational analysis of phosphorylated β-(1→2)
           linked mannosides
    • Abstract: Publication date: 13 January 2014
      Source:Carbohydrate Research, Volume 383
      Author(s): Jani Rahkila , Filip S. Ekholm , Rajib Panchadhayee , Ana Ardá , Francisco Javier Cañada , Jesús Jiménez-Barbero , Reko Leino
      Phosphorylated β-(1→2)-oligomannosides are found on the cell surface of several Candida species, including Candida albicans (an opportunistic pathogen). These molecules are believed to take part in the invasion process of fungal infections, which in the case of C. albicans can lead to severe bloodstream infections and death, and can therefore be considered important from a biological standpoint. Understanding the mechanism of their action requires access to the corresponding oligosaccharide model compounds in pure form. In the present work, synthesis of the model core structures involved in the invasion process of C. albicans, consisting of phosphorylated β-(1→2)-linked mannotriose and tetraose, is reported. In order to elucidate the nature of these molecules in more detail, an extensive NMR-spectroscopic study encompassing complete spectral characterization, conformational analysis and molecular modelling was performed. The obtained results were also compared to similar chemical entities devoid of the charged phosphate group.
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      PubDate: 2013-11-29T00:05:39Z
       
  • Synthesis, Characterization, and Comparative Analysis of Amylose-Guest
           Complexes Prepared by Microwave Irradiation
    • Abstract: Publication date: Available online 22 November 2013
      Source:Carbohydrate Research
      Author(s): Lisa M. Ryno , Yael Levine , Peter M. Iovine
      The preparation and characterization of amylose•small molecule complexes is a heavily researched area. There are few reports, however, that compare complexation efficiencies across a matrix of different amylose hosts and guests. We present herein a detailed account of using microwave irradiation to prepare amylose•small molecule complexes in water. Microwave heating reduced the time required to prepare these amylose complexes from hours to minutes. We characterized not only the quantity of complex for each amylose•guest pairing but also the loading of small molecule guest in that complex. Amylose•1-naphthol complexes were found to have the highest loading density compared with other hydrophobic guests studied; in the case of 1-naphthol, there was a linear dependence of guest loading on amylose molecular weight. In addition, complexes featuring 1-naphthol were the most ordered as judged by powder x-ray diffraction (XRD) and differential scanning calorimetry. Further, powder XRD analysis of the microwave-prepared complexes revealed that many contained mixtures of V-form (single helix) and B-form (double helical) amylose. Lastly, untreated Hylon VII complexed the widest variety of small molecules with the overall greatest efficiency.
      Graphical abstract image Highlights

      PubDate: 2013-11-24T23:10:18Z
       
  • ortho-Methylphenyl Thioglycosides as Glycosyl Building Blocks for
           Preactivation-Based Oligosaccharide Synthesis
    • Abstract: Publication date: Available online 22 November 2013
      Source:Carbohydrate Research
      Author(s): Peng Peng , De-Cai Xiong , Xin-Shan Ye
      Thioglycosides are widely used in orthogonal glycosylation, armed-disarmed chemoselective glycosylation, and preactivation-based glycosylation. Nevertheless, aglycon transfer occasionally occurred in the glycosylation process of thioglycosides. This problem was also encountered in preactivation-based reactions, which limited the applications of preactivation-based glycosylation to some extent. To tackle this problem, sterically hindered aglycon ortho-methylphenylthioglycosides were introduced as glycosyl building blocks. These thioglycosides prevented the aglycon transfer and enhanced the efficiency of glycosyl coupling reactions, especially in the reactions of disarmed donors with armed acceptors. Moreover, these thioglycosides were employed in preactivation-based one-pot oligosaccharide assembly.
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      PubDate: 2013-11-24T23:10:18Z
       
  • Planococcus maritimus VITP21 synthesizes
           (2-acetamido-2-deoxy-α-D-glucopyranosyl)-(1→2)-β-D-fructofuranose
           under osmotic stress: a novel protein stabilizing sugar-osmolyte
    • Abstract: Publication date: Available online 23 November 2013
      Source:Carbohydrate Research
      Author(s): Nidhya Nadarajan Joghee , Jayaraman Gurunathan
      A halotolerant bacterium, Planococcus maritimus VITP21 isolated from a saltern region in Kumta along the Arabian Sea Coast of India was found to have increased cellular levels of sugars (up to 2.3 fold) under osmotic stress when grown in minimal medium with glucose as the sole carbon and energy source supplemented with 10% w/v NaCl. The major sugar-osmolyte which increased with the concentration of NaCl in the growth medium was purified and characterized using various nuclear magnetic resonance spectroscopy techniques. The sugar was found to be similar to sucrose but with the C-2 hydroxyl group of the glucose ring substituted with acetamido group, which is not previously reported for its natural synthesis by any other organism. This novel sugar, (2-acetamido-2-deoxy-α-D-glucopyranosyl)-(1→2)-β-D-fructofuranose, exhibited stabilizing effect on a model protein α-amylase by increasing the apparent midpoint transition, onset temperature of denaturation and free energy of thermal unfolding.
      Graphical abstract image Highlights

      PubDate: 2013-11-24T23:10:18Z
       
  • Total synthesis of a sialyl lewisx derivative for the diagnosis of cancer
    • Abstract: Publication date: Available online 23 November 2013
      Source:Carbohydrate Research
      Author(s): Dan Lu , Yongzhou Hu , Xianran He , Matthieu Sollogoub , Yongmin Zhang
      The total synthesis of aminoethyl glycoside of sialyl Lewisx (sLex) is described. A galactose donor was condensed with a diol of glucosamine to afford regioselectively a β1,4 linked disaccharide, which was further stereoselectively fucosylated to provide a protected Lewisx trisaccharide. After chemical modification, the trisaccharide was sialylated to give regio- and stereoselectively an azidoethly glycoside of sLex. Finally, deprotection and azide reduction afforded the target compound. This compound will be coupled with protein and then be used to conduct further preclinical studies for the diagnosis of cancer.
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      PubDate: 2013-11-24T23:10:18Z
       
  • Conversion of yeast mannan polysaccharide in mannose oligosaccharides with
           a thiopropargyl linker at the pseudo-reducing end
    • Abstract: Publication date: 13 January 2014
      Source:Carbohydrate Research, Volume 383
      Author(s): Alberto M. Marzaioli , Emiliano Bedini , Rosa Lanzetta , Michelangelo Parrilli , Cristina De Castro
      Polysaccharides are useful sources of preformed glycosyl linkages and therefore convenient building blocks can be prepared from them upon application of a proper degradation and derivatization scheme. Following this idea, the α-(1→6) linkages of this polysaccharide were broken applying acetolysis reaction and the pseudo-reducing position of the resulting acetylated mannose oligosaccharides was functionalized with a thiopropargyl appendage through thiourea activation of the related glycosyl iodides. Deacetylation of the final products and optimization of the purification procedures are discussed. The best yields were observed combining size exclusion chromatography and HPLC. Nine different oligosaccharides, from mono- to tetrasaccharides, mainly α-configured at the pseudo-reducing terminal, were obtained in pure form, presenting the propargyl appendage, a feature that makes them suitable substrates for successive functionalizations.
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      PubDate: 2013-11-24T23:10:18Z
       
  • Pyrrolidine-type iminosugars from leaves of Suregada glomerulata
    • Abstract: Publication date: Available online 19 November 2013
      Source:Carbohydrate Research
      Author(s): Ren-Yi Yan , Hong-Qing Wang , Jie Kang , Ruo-Yun Chen
      Phytochemical investigation of the H2O extract of leaves of Suregada glomerulata led to the isolation of ten pyrrolidine-type iminosugars. The chemical structures of the six new compounds (4-6, 8-10) were elucidated as 2,5-imino-2,4,5-trideoxy-D-manno-heptitol (4-deoxy-homoDMDP) (4), 2,5-imino-2,4,5-trideoxy-D-gulo-heptitol(5), 2,5-imino- 2,4,5,6-tetradeoxy-D-gulo-heptitol (6), 6-C-butyl-4-deoxy-DMDP (8), 6-C-(8-hydroxyoctyl)-DMDP (9), and 6-C-(8-hydroxyoctyl)-2,5-dideoxy-2,5-imino-D- galactitol (10), respectively, on the basis of spectroscopic data analysis (NMR and HRESIMS). Compounds 4-6 and 8 were characterized as rarely seen 4-deoxy pyrrolidine-type iminosugar. Pyrrolidine-type iminosugars with a long-side chain have been found in the restrictive plant families Moraceae, Campanulaceae, and Hyacinthaceae. The discovery of compounds 9 and 10 with a C8 side chain from S. glomerulata (Euphorbiaceae) expands the range of distribution for the iminosugars in plants. The 8-hydroxyoctyl side-chain represents a new addition for the molecular diversity of iminosugars. The compounds 1–10 were evaluated for inhibitory activity against rat intestinal α-glucosidase. However, all the test compounds showed no significant inhibitory activities to the glucosidase.
      Graphical abstract image

      PubDate: 2013-11-21T00:05:37Z
       
  • Examination of the influence of C5-hydroxymethyl group and configurations
           of hydroxyl groups at C2, C3 and C4 stereocentres on the N-glycosidic
           torsion: Synthesis and X-ray crystallographic investigation of
           N-(D-ribopyranosyl)alkanamides as N-glycoprotein linkage region analogs
    • Abstract: Publication date: Available online 18 November 2013
      Source:Carbohydrate Research
      Author(s): Amrita Srivastava , Manoharan Mathiselvam , Babu Varghese , Duraikkannu Loganathan
      N-Linked glycosylation is not only present in eukaryotes but also occurs in archaea and bacteria and is mainly characterized by the β-glucosylamine linkage to the asparagine (GlcNAcβAsn). Earlier crystallographic studies aimed at understanding the structural significance of the linkage region constituents revealed that N-glycosidic torsion, ϕN is influenced considerably by variation in the glycan part as compared to the aglycon moiety. The ϕN value observed for XylβNHAc deviated maximum as compared to that of the model compound, GlcNAcβNHAc. The present work was undertaken to assess the influence of ribose on the N-glycosidic torsions and molecular assembly. Several ribopyranosyl alkanamides have been synthesized and crystal structures of three of them have been solved. A comprehensive crystal structure analysis of ribosyl alkanamides along with xylosyl and arabinosyl alkanamides showed the wide range of deviations in their ϕN values as compared to the negligible deviation shown by hexopyranosyl alkanamides. This study revealed the importance of C5-hydroxymethyl group and hydroxyl group configurations at C2, C3 and C4 stereocentres in controlling the N-glycosidic torsions.
      Graphical abstract image Highlights

      PubDate: 2013-11-21T00:05:37Z
       
  • The Interaction of Enoxaparin and Fondaparinux with Calcium
    • Abstract: Publication date: Available online 19 November 2013
      Source:Carbohydrate Research
      Author(s): Károly Mazák , Consuelo N. Beecher , Márta Kraszni , Cynthia K. Larive
      The main sites of calcium binding were determined for the low molecular weight heparin drug enoxaparin and the synthetic pentasaccharide Arixtra (fondaparinux). [1H,13C] HSQC pH titrations were carried out to characterize the acid-base properties of these samples both in the presence and absence of calcium. The differences in the titration curves were used to determine the structural components of enoxaparin and fondaparinux responsible for Ca2+ binding. In enoxaparin both unsubstituted and 2-O-sulfated iduronic acid residues are important in calcium binding and the presence of the 2-O-sulfo group does not seem to influence the Ca2+ binding capability of the iduronate ring. In fondaparinux changes in chemical shifts upon Ca2+ binding were smaller than observed for enoxaparin, and were observed for both the glucuronic acid and 2-O-sulfated iduronic acid residues. In enoxaparin significant perturbations of the chemical shift of the N-sulfoglucosamine anomeric carbon in residues connected to 2-O-sulfated iduronic acid were detected on Ca2+ binding, however it was not possible to determine whether these changes reflect direct involvement in calcium complexation or result from through space interactions or conformational changes.
      Graphical abstract image

      PubDate: 2013-11-21T00:05:37Z
       
  • Structure elucidation of capsular polysaccharides from Streptococcus
           pneumoniae serotype 33C, 33D and revised structure of serotype 33B
    • Abstract: Publication date: Available online 19 November 2013
      Source:Carbohydrate Research
      Author(s): Fiona L. Lin , Evgeny Vinogradov , Chenghua Deng , Sandra Zeller , Lynn Phelan , Bruce A. Green , Kathrin U. Jansen , Viliam Pavliak
      We report herein the previously unknown structures of the pneumococcal capsular polysaccharides serotype 33C and 33D, and a revised structure of serotype 33B. The syntenic pair 33B/33D have nearly identical polysaccharide repeat units with the exception of one sugar residue (→2-α-Glcp in 33B and →2-α-Galp in 33D). Serotype 33C is structurally more similar to 33B/33D than 33A/33F, in that it also possesses a backbone ribitol-phosphate group and a →3-β-GalpNAc residue, both of which are absent in the repeat units of 33A/33F. Serotype 33C is notably different from all other serogroup 33 polysaccharides, as there is no →3-β-Glcp residue and the location of the O-acetylation of the →5-β-Galf residue (O-6) differs from the other serogroup 33 polysaccharides (O-2). This completes the structural assignments of polysaccharides within serogroup 33 and provides a framework for understanding the recognition of epitopes by serogroup 33 typing sera based on observed cross-reactivities reported in the literature.
      Graphical abstract image Highlights

      PubDate: 2013-11-21T00:05:37Z
       
  • Production of chitooligosaccharides from Rhizopus oligosporus NRRL2710
           cells by chitosanase digestion
    • Abstract: Publication date: 13 January 2014
      Source:Carbohydrate Research, Volume 383
      Author(s): Maria Mahata , Shoko Shinya , Eiko Masaki , Takashi Yamamoto , Takayuki Ohnuma , Ryszard Brzezinski , Tapan K. Mazumder , Kazuhiko Yamashita , Kazue Narihiro , Tamo Fukamizo
      The intact cells of Rhizopus oligosporus NRRL2710, whose cell walls are abundant source of N-acetylglucosamine (GlcNAc) and glucosamine (GlcN), were digested with three chitinolytic enzymes, a GH-46 chitosanase from Streptomyces sp. N174 (CsnN174), a chitinase from Pyrococcus furiosus, and a chitinase from Trichoderma viride, respectively. Solubilization of the intact cells by CsnN174 was found to be the most efficient from solid state CP/MAS 13C NMR spectroscopy. Chitosanase products from Rhizopus cells were purified by cation exchange chromatography on CM-Sephadex C-25 and gel-filtration on Cellulofine Gcl-25m. NMR and MALDI-TOF-MS analyses of the purified products revealed that GlcN–GlcNAc, (GlcN)2–GlcNAc, and (GlcN)2 were produced by the enzymatic digestion of the intact cells. The chitosanase digestion of Rhizopus cells was found to be an excellent system for the conversion of fungal biomass without any environmental impact.
      Graphical abstract image

      PubDate: 2013-11-17T00:05:45Z
       
  • Synthesis of modified Trichinella spiralis disaccharide epitopes and a
           comparison of their recognition by chemical mapping and saturation
           transfer difference NMR
    • Abstract: Publication date: Available online 1 November 2013
      Source:Carbohydrate Research
      Author(s): Lina Cui , Chang-Chun Ling , Joanna Sadowska , David R. Bundle
      A rat monoclonal antibody 9D4 raised against the cell surface N-glycan of the parasite Trichinella spirallis protects rats against further infection. The terminal disaccharide β-D-Tyvp(1→3)β-D-GalNAcp (2) represents the immunodominant portion of the antigenic determinant. Chemical mapping of the antibody binding site by functional group modification employing monodeoxy and mono-O-methyl congeners identified key polar contacts and topography of the bound disacccharide. We report here a comparison of the chemical mapping studies with the antigen topography inferred from saturation transfer difference (STD) NMR experiments. During chemical mapping several congeners of compound 2 showed substantially enhanced binding. Pairing of these functional group modifications to create derivatives 6 and 7 did not show additive free energy gains and STD NMR data point to small variations in mode of binding as a probable cause. Improved syntheses of disaccharides 2-7 are reported.
      Graphical abstract image Highlights

      PubDate: 2013-11-05T00:12:48Z
       
  • Efficient One-pot Synthesis of Tigogenin Saponins and Their Antitumor
           Activities
    • Abstract: Publication date: Available online 30 October 2013
      Source:Carbohydrate Research
      Author(s): Guofeng Gu , Lian An , Min Fang , Zhongwu Guo
      An efficient synthesis of naturally occurring tigogenin triglycoside 1a and its three derivatives 1b-d bearing different carbohydrate moieties, as well as their antitumor activities, is described. Partially protected thiogalactosides bearing unprotected 2,4-OH or 4-OH groups were used to facilitate regioselective reactions for one-pot sequential multi-step glycosylation, which has significantly simplified the target molecule synthesis. The synthetic saponins 1a-d exhibited much higher anti-tumor activities than the positive control cisplatin against the human epithelial cervical cancer cell (HeLa) as evaluated by CCK-8 assay.
      Graphical abstract image

      PubDate: 2013-11-01T00:05:44Z
       
 
 
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