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  Subjects -> CHEMISTRY (Total: 843 journals)
    - ANALYTICAL CHEMISTRY (51 journals)
    - CHEMISTRY (594 journals)
    - CRYSTALLOGRAPHY (21 journals)
    - ELECTROCHEMISTRY (25 journals)
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CHEMISTRY (594 journals)                  1 2 3 | Last

Showing 1 - 200 of 735 Journals sorted alphabetically
2D Materials     Hybrid Journal   (Followers: 8)
Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement     Hybrid Journal   (Followers: 26)
ACS Catalysis     Full-text available via subscription   (Followers: 34)
ACS Chemical Neuroscience     Full-text available via subscription   (Followers: 18)
ACS Combinatorial Science     Full-text available via subscription   (Followers: 23)
ACS Macro Letters     Full-text available via subscription   (Followers: 23)
ACS Medicinal Chemistry Letters     Full-text available via subscription   (Followers: 39)
ACS Nano     Full-text available via subscription   (Followers: 233)
ACS Photonics     Full-text available via subscription   (Followers: 11)
ACS Synthetic Biology     Full-text available via subscription   (Followers: 21)
Acta Chemica Iasi     Open Access   (Followers: 2)
Acta Chimica Sinica     Full-text available via subscription   (Followers: 1)
Acta Chimica Slovaca     Open Access   (Followers: 1)
Acta Chromatographica     Full-text available via subscription   (Followers: 9)
Acta Facultatis Medicae Naissensis     Open Access  
Acta Metallurgica Sinica (English Letters)     Hybrid Journal   (Followers: 5)
Acta Scientifica Naturalis     Open Access   (Followers: 2)
adhäsion KLEBEN & DICHTEN     Hybrid Journal   (Followers: 5)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 8)
Adsorption Science & Technology     Full-text available via subscription   (Followers: 5)
Advanced Functional Materials     Hybrid Journal   (Followers: 50)
Advanced Science Focus     Free   (Followers: 3)
Advances in Chemical Engineering and Science     Open Access   (Followers: 55)
Advances in Chemical Science     Open Access   (Followers: 13)
Advances in Chemistry     Open Access   (Followers: 15)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 18)
Advances in Drug Research     Full-text available via subscription   (Followers: 22)
Advances in Enzyme Research     Open Access   (Followers: 9)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 16)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 9)
Advances in Materials Physics and Chemistry     Open Access   (Followers: 20)
Advances in Nanoparticles     Open Access   (Followers: 15)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 15)
Advances in Polymer Science     Hybrid Journal   (Followers: 41)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 17)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 20)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 5)
Advances in Science and Technology     Full-text available via subscription   (Followers: 12)
African Journal of Bacteriology Research     Open Access  
African Journal of Chemical Education     Open Access   (Followers: 2)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 7)
Agrokémia és Talajtan     Full-text available via subscription   (Followers: 2)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 3)
AMB Express     Open Access   (Followers: 1)
Ambix     Hybrid Journal   (Followers: 3)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 67)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 14)
American Journal of Chemistry     Open Access   (Followers: 27)
American Journal of Plant Physiology     Open Access   (Followers: 14)
American Mineralogist     Hybrid Journal   (Followers: 14)
Analyst     Full-text available via subscription   (Followers: 40)
Angewandte Chemie     Hybrid Journal   (Followers: 170)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 215)
Annales UMCS, Chemia     Open Access   (Followers: 1)
Annals of Clinical Chemistry and Laboratory Medicine     Open Access   (Followers: 3)
Annual Reports in Computational Chemistry     Full-text available via subscription   (Followers: 3)
Annual Reports Section A (Inorganic Chemistry)     Full-text available via subscription   (Followers: 4)
Annual Reports Section B (Organic Chemistry)     Full-text available via subscription   (Followers: 8)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 12)
Annual Review of Food Science and Technology     Full-text available via subscription   (Followers: 15)
Anti-Infective Agents     Hybrid Journal   (Followers: 3)
Antiviral Chemistry and Chemotherapy     Hybrid Journal  
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 7)
Applied Spectroscopy     Full-text available via subscription   (Followers: 23)
Applied Surface Science     Hybrid Journal   (Followers: 28)
Arabian Journal of Chemistry     Open Access   (Followers: 6)
ARKIVOC     Open Access   (Followers: 2)
Asian Journal of Biochemistry     Open Access   (Followers: 1)
Atomization and Sprays     Full-text available via subscription   (Followers: 4)
Australian Journal of Chemistry     Hybrid Journal   (Followers: 7)
Autophagy     Hybrid Journal   (Followers: 2)
Avances en Quimica     Open Access   (Followers: 1)
Biochemical Pharmacology     Hybrid Journal   (Followers: 10)
Biochemistry     Full-text available via subscription   (Followers: 304)
Biochemistry Insights     Open Access   (Followers: 6)
Biochemistry Research International     Open Access   (Followers: 6)
BioChip Journal     Hybrid Journal  
Bioinorganic Chemistry and Applications     Open Access   (Followers: 9)
Bioinspired Materials     Open Access   (Followers: 5)
Biointerface Research in Applied Chemistry     Open Access   (Followers: 2)
Biointerphases     Open Access   (Followers: 1)
Biology, Medicine, & Natural Product Chemistry     Open Access   (Followers: 1)
Biomacromolecules     Full-text available via subscription   (Followers: 19)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 10)
Biomedical Chromatography     Hybrid Journal   (Followers: 6)
Biomolecular NMR Assignments     Hybrid Journal   (Followers: 3)
BioNanoScience     Partially Free   (Followers: 5)
Bioorganic & Medicinal Chemistry     Hybrid Journal   (Followers: 114)
Bioorganic & Medicinal Chemistry Letters     Hybrid Journal   (Followers: 96)
Bioorganic Chemistry     Hybrid Journal   (Followers: 10)
Biopolymers     Hybrid Journal   (Followers: 18)
Biosensors     Open Access   (Followers: 2)
Biotechnic and Histochemistry     Hybrid Journal   (Followers: 1)
Bitácora Digital     Open Access  
Boletin de la Sociedad Chilena de Quimica     Open Access  
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 2)
Bulletin of the Chemical Society of Japan     Full-text available via subscription   (Followers: 24)
Bulletin of the Korean Chemical Society     Hybrid Journal   (Followers: 1)
C - Journal of Carbon Research     Open Access   (Followers: 3)
Cakra Kimia (Indonesian E-Journal of Applied Chemistry)     Open Access  
Canadian Association of Radiologists Journal     Full-text available via subscription   (Followers: 3)
Canadian Journal of Chemistry     Hybrid Journal   (Followers: 10)
Canadian Mineralogist     Full-text available via subscription   (Followers: 4)
Carbohydrate Research     Hybrid Journal   (Followers: 26)
Carbon     Hybrid Journal   (Followers: 66)
Catalysis for Sustainable Energy     Open Access   (Followers: 7)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 8)
Catalysis Science and Technology     Free   (Followers: 7)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 3)
Catalysts     Open Access   (Followers: 8)
Cellulose     Hybrid Journal   (Followers: 7)
Cereal Chemistry     Full-text available via subscription   (Followers: 4)
ChemBioEng Reviews     Full-text available via subscription   (Followers: 1)
ChemCatChem     Hybrid Journal   (Followers: 8)
Chemical and Engineering News     Free   (Followers: 13)
Chemical Bulletin of Kazakh National University     Open Access  
Chemical Communications     Full-text available via subscription   (Followers: 70)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 23)
Chemical Research in Chinese Universities     Hybrid Journal   (Followers: 3)
Chemical Research in Toxicology     Full-text available via subscription   (Followers: 19)
Chemical Reviews     Full-text available via subscription   (Followers: 189)
Chemical Science     Open Access   (Followers: 22)
Chemical Technology     Open Access   (Followers: 16)
Chemical Vapor Deposition     Hybrid Journal   (Followers: 5)
Chemical Week     Full-text available via subscription   (Followers: 8)
Chemie in Unserer Zeit     Hybrid Journal   (Followers: 58)
Chemie-Ingenieur-Technik (Cit)     Hybrid Journal   (Followers: 26)
ChemInform     Hybrid Journal   (Followers: 8)
Chemistry & Biodiversity     Hybrid Journal   (Followers: 6)
Chemistry & Biology     Full-text available via subscription   (Followers: 30)
Chemistry & Industry     Hybrid Journal   (Followers: 5)
Chemistry - A European Journal     Hybrid Journal   (Followers: 140)
Chemistry - An Asian Journal     Hybrid Journal   (Followers: 15)
Chemistry and Materials Research     Open Access   (Followers: 18)
Chemistry Central Journal     Open Access   (Followers: 4)
Chemistry Education Research and Practice     Free   (Followers: 5)
Chemistry in Education     Open Access   (Followers: 9)
Chemistry International     Hybrid Journal   (Followers: 2)
Chemistry Letters     Full-text available via subscription   (Followers: 44)
Chemistry of Materials     Full-text available via subscription   (Followers: 264)
Chemistry of Natural Compounds     Hybrid Journal   (Followers: 9)
Chemistry World     Full-text available via subscription   (Followers: 22)
Chemistry-Didactics-Ecology-Metrology     Open Access   (Followers: 1)
ChemistryOpen     Open Access   (Followers: 2)
Chemkon - Chemie Konkret, Forum Fuer Unterricht Und Didaktik     Hybrid Journal  
Chemoecology     Hybrid Journal   (Followers: 4)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 15)
Chemosensors     Open Access  
ChemPhysChem     Hybrid Journal   (Followers: 9)
ChemPlusChem     Hybrid Journal   (Followers: 2)
ChemTexts     Hybrid Journal  
CHIMIA International Journal for Chemistry     Full-text available via subscription   (Followers: 2)
Chinese Journal of Chemistry     Hybrid Journal   (Followers: 6)
Chinese Journal of Polymer Science     Hybrid Journal   (Followers: 10)
Chromatographia     Hybrid Journal   (Followers: 24)
Clay Minerals     Full-text available via subscription   (Followers: 10)
Cogent Chemistry     Open Access  
Colloid and Interface Science Communications     Open Access  
Colloid and Polymer Science     Hybrid Journal   (Followers: 10)
Colloids and Surfaces B: Biointerfaces     Hybrid Journal   (Followers: 7)
Combinatorial Chemistry & High Throughput Screening     Hybrid Journal   (Followers: 4)
Combustion Science and Technology     Hybrid Journal   (Followers: 18)
Comments on Inorganic Chemistry: A Journal of Critical Discussion of the Current Literature     Hybrid Journal   (Followers: 2)
Composite Interfaces     Hybrid Journal   (Followers: 6)
Comprehensive Chemical Kinetics     Full-text available via subscription   (Followers: 2)
Comptes Rendus Chimie     Full-text available via subscription  
Comptes Rendus Physique     Full-text available via subscription   (Followers: 1)
Computational and Theoretical Chemistry     Hybrid Journal   (Followers: 9)
Computational Biology and Chemistry     Hybrid Journal   (Followers: 12)
Computational Chemistry     Open Access   (Followers: 2)
Computers & Chemical Engineering     Hybrid Journal   (Followers: 9)
Coordination Chemistry Reviews     Full-text available via subscription   (Followers: 2)
Copernican Letters     Open Access   (Followers: 1)
Critical Reviews in Biochemistry and Molecular Biology     Hybrid Journal   (Followers: 5)
Crystal Structure Theory and Applications     Open Access   (Followers: 3)
CrystEngComm     Full-text available via subscription   (Followers: 13)
Current Catalysis     Hybrid Journal   (Followers: 2)
Current Metabolomics     Hybrid Journal   (Followers: 5)
Current Opinion in Colloid & Interface Science     Hybrid Journal   (Followers: 9)
Current Research in Chemistry     Open Access   (Followers: 8)
Current Science     Open Access   (Followers: 60)
Dalton Transactions     Full-text available via subscription   (Followers: 22)
Detection     Open Access   (Followers: 2)
Developments in Geochemistry     Full-text available via subscription   (Followers: 2)
Diamond and Related Materials     Hybrid Journal   (Followers: 12)
Dislocations in Solids     Full-text available via subscription  
Doklady Chemistry     Hybrid Journal  
Drying Technology: An International Journal     Hybrid Journal   (Followers: 4)
Eclética Química     Open Access   (Followers: 1)
Ecological Chemistry and Engineering S     Open Access   (Followers: 3)
Ecotoxicology and Environmental Contamination     Open Access  
Educación Química     Open Access   (Followers: 1)
Education for Chemical Engineers     Hybrid Journal   (Followers: 5)
EJNMMI Radiopharmacy and Chemistry     Open Access  
Elements     Full-text available via subscription   (Followers: 3)
Environmental Chemistry     Hybrid Journal   (Followers: 7)
Environmental Chemistry Letters     Hybrid Journal   (Followers: 4)
Environmental Science & Technology Letters     Full-text available via subscription   (Followers: 5)
Environmental Science : Nano     Partially Free   (Followers: 1)
Environmental Toxicology & Chemistry     Hybrid Journal   (Followers: 17)

        1 2 3 | Last

Journal Cover Carbohydrate Research
  [SJR: 0.612]   [H-I: 98]   [26 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0008-6215 - ISSN (Online) 0008-6215
   Published by Elsevier Homepage  [3043 journals]
  • Synthesis of LewisX-O-core-1 threonine: A building block for O-linked
           LewisX glycopeptides
    • Abstract: Publication date: Available online 10 October 2017
      Source:Carbohydrate Research
      Author(s): Mohammed Y.R. Sardar, Venkata R. Krishnamurthy, Simon Park, Appi R. Mandhapati, Walter J. Wever, Dayoung Park, Richard D. Cummings, Elliot L. Chaikof
      Lewis X (LeX) is a branched trisaccharide Galβ1→4(Fucα1→3)GlcNAc that is expressed on many cell surface glycoproteins and plays critical roles in innate and adaptive immune responses. However, efficient synthesis of glycopeptides bearing LeX remains a major limitation for structure-function studies of the LeX determinant. Here we report a total synthesis of a LeX pentasaccharide 1 using a regioselective 1-benzenesulfinyl piperidine/triflic anhydride promoted [3 + 2] glycosylation. The presence of an Fmoc-threonine amino acid facilitates incorporation of the pentasaccharide in solid phase peptide synthesis, providing a route to diverse O-linked LeX glycopeptides. The described approach is broadly applicable to the synthesis of a variety of complex glycopeptides containing O-linked LeX or sialyl LewisX (sLeX).
      Graphical abstract image

      PubDate: 2017-10-11T14:12:53Z
       
  • Chemical remodeling cell surface glycans for immunotargeting of tumor
           cells
    • Abstract: Publication date: Available online 10 October 2017
      Source:Carbohydrate Research
      Author(s): Xuexia Li, Xiaoyan Xu, Xiongjian Rao, Yinping Tian, Wen Yi
      Recruitment of human endogenous antibodies to target and eliminate tumor cells is a promising therapeutic strategy in the biomedical field. Current antibody-recruiting molecules are typically bi-functional agents that utilize cell-surface receptor binding property for targeting. This approach has intrinsic limitations due to the heterogeneity of tumor cells and the limited number of receptors on the cell surface. Here we report a targeting strategy based on remodeling of cell surface glycans through metabolic engineering and bioorthogonal chemical ligation. In vitro cultured tumor cells and in vivo xenograft tumors were actively remodeled with rhamnose carbohydrate epitopes, which were capable of recruiting endogenous anti-rhamnose antibodies and activating complement-mediated cell cytotoxicity. This study highlights the therapeutic potential for modulating endogenous immune response through cell-surface glycan engineering.
      Graphical abstract image

      PubDate: 2017-10-11T14:12:53Z
       
  • Synthesis and binding affinity analysis of α1-2- and α1-6-O/S-linked
           dimannosides for the elucidation of sulfur in glycosidic bonds using
           quartz crystal microbalance sensors
    • Abstract: Publication date: Available online 9 October 2017
      Source:Carbohydrate Research
      Author(s): Oscar Norberg, Bin Wu, Niranjan Thota, Jiantao Ge, Germain Fauquet, Ann-Kathrin Saur, Teodor Aastrup, Hai Dong, Mingdi Yan, Olof Ramström
      The role of sulfur in glycosidic bonds has been evaluated using quartz crystal microbalance methodology. Synthetic routes towards α1-2- and α1-6-linked dimannosides with S- or O-glycosidic bonds have been developed, and the recognition properties assessed in competition binding assays with the cognate lectin concanavalin A. Mannose-presenting QCM sensors were produced using photoinitiated, nitrene-mediated immobilization methods, and the subsequent binding study was performed in an automated flow-through instrumentation, and correlated with data from isothermal titration calorimetry. The recorded K d-values corresponded well with reported binding affinities for the O-linked dimannosides with affinities for the α1-2-linked dimannosides in the lower micromolar range. The S-linked analogs showed slightly disparate effects, where the α1-6-linked analog showed weaker affinity than the O-linked dimannoside, as well as positive apparent cooperativity, whereas the α1-2-analog displayed very similar binding compared to the O-linked structure.
      Graphical abstract image

      PubDate: 2017-10-11T14:12:53Z
       
  • 1H NMR studies of molecular interaction of D-glucosamine and
           N-acetyl-D-glucosamine with capsaicin in aqueous and non-aqueous media
    • Abstract: Publication date: Available online 29 September 2017
      Source:Carbohydrate Research
      Author(s): Inocencio Higuera-Ciapara, Claudia Virués, Marcela Jiménez-Chávez, Evelin Martínez-Benavidez, Javier Hernández, Zaira Domínguez, Roberto López-Rendón, Enrique F. Velázquez, Motomichi Inoue
      Complex formation of D-glucosamine (Gl) and N-acetyl-D-glucosamine (AGl) with capsaicin (Cp) were studied by 1H NMR titrations in H2O-d2 and DMSO-d6; capsaicin is the major bioactive component of chili peppers. Every titration curve has been interpreted by formulating a suitable model for the reaction equilibrium, to elucidate intermolecular interactions. In DMSO, glucosamine cations associate with each other to yield linear aggregates, and undergo pseudo-1:1-complexation with capsaicin, the formation constant being ca. 30 M−1. N-Acetylglucosamine, without self-association, forms a 2:1-complex AGl2Cp with the stability of ca. 70 M−2. These complexations are achieved by intermolecular hydrogen bonds. In D2O, glucosamine undergoes reversible protonation equilibrium between Gl0 and GlH+ with the logarithmic protonation constants log K D  = 8.63 for α-glucosamine and 8.20 for β-isomer. Both anomeric isomers of deprotonated glucosamine form Gl0Cp-type complexes of capsaicin, in a competitive manner, with a formation constant of 1040 M−1 for the α-glucosamine complex and 830 M−1 for the β-complex; the anomeric carbons result in the difference in thermodynamic stability. The reactant molecules are closed up by the solvent-exclusion effect and/or the van der Waals interaction; the resulting pair is stabilized by intermolecular hydrogen bonding within a local water-free space between the component molecules. By contrast, neither protonated glucosamine (GlH+) nor N-acetylglucosamine yields a capsaicin complex with the definite stoichiometry. The monosaccharides recognize capsaicin under only a controlled condition; the same phenomena are predicted for biological systems and nanocarriers based on polysaccharides such as chitosan.
      Graphical abstract image

      PubDate: 2017-10-03T13:54:57Z
       
  • Tracking the leaving group in the remote activation of
           O-2-[(propan-2-yl)sulfinyl]benzyl (OPSB) glycoside
    • Abstract: Publication date: Available online 28 September 2017
      Source:Carbohydrate Research
      Author(s): Wei Chen, Jing Zeng, Hao Wang, Xiong Xiao, Lingkui Meng, Qian Wan
      In our recently developed interrupted Pummerer reaction mediated glycosylation with O-2-[(propan-2-yl)sulfinyl]benzyl (OPSB) glycosides as glycosyl donors, the anomeric leaving group was recovered as a benzyl alcohol which didn't affect the glycosylation efficiency. To investigate the mechanism of the occurrence of this alcohol, an 18O isotopic labeling reaction was carried out to track the leaving group. It was found that the benzyl alcohol was generated during the aqueous work up process from an inactive cyclic oxo-sulfonium ion intermediate. It was also proved that H2O prefer to attack the sulfur atom position during the hydrolysis of the intermediate.
      Graphical abstract image

      PubDate: 2017-10-03T13:54:57Z
       
  • Preparation of new β-D-xyloside- and β-D-xylobioside-based ionic liquids
           through chemical and/or enzymatic reactions
    • Abstract: Publication date: Available online 23 September 2017
      Source:Carbohydrate Research
      Author(s): S. Gatard, R. Plantier-Royon, C. Rémond, M. Muzard, C. Kowandy, S. Bouquillon
      Several tetraalkylphosphonium and tetraalkylammonium salts containing xyloside- and xylobioside-based anionic moieties have been prepared. Two stereoselective routes have been developed: i) a chemical pathway in four steps from D-xylose, and ii) a chemoenzymatic pathway directly from biomass-derived xylans. These salts displayed interesting properties as ionic liquids. Their structures have been correlated to their thermal properties (melting, glass transition and decomposition temperatures).
      Graphical abstract image

      PubDate: 2017-09-26T13:45:26Z
       
  • Structural characterisation of the capsular polysaccharide expressed by
           Burkholderia thailandensis strain E555:: wbiI (pKnock-KmR) and assessment
           of the significance of the 2-O-acetyl group in immune protection
    • Abstract: Publication date: Available online 21 September 2017
      Source:Carbohydrate Research
      Author(s): Marc Bayliss, Matthew I. Donaldson, Sergey A. Nepogodiev, Giulia Pergolizzi, Andrew E. Scott, Nicholas J. Harmer, Robert A. Field, Joann L. Prior
      Burkholderia pseudomallei and its close relative B. mallei are human pathogens that are classified as Tier 1 bio-threat agents. Both organisms have previously been shown to constitutively produce a capsular polysaccharide (CPS) that is both a virulence determinant and protective antigen. Extraction and purification of CPS for use as a potential vaccine candidate requires containment level 3 laboratories which is expensive and time-consuming. B. thailandensis strain E555 is closely related to B. pseudomallei and B. mallei, but is non-pathogenic to humans and based on immunological cross-reactivity has previously been shown to express a B. pseudomallei-like CPS. In this study, capsular polysaccharide isolated from an O-antigen deficient strain of B. thailandensis E555 was identified by 1H and 13C NMR spectroscopy as -3-)-2-O-acetyl-6-deoxy-β-d-manno-heptopyranose-(-1, and identical to that produced by B. pseudomallei. This was further substantiated by anti-CPS monoclonal antibody binding. In connection with the production of CPS fragments for use in glycoconjugate vaccines, we set out to assess the importance or otherwise of the CPS 2-OAc groups in immune protection. To this end conjugates of the native and de-O-acetylated CPS with the Hc fragment of tetanus toxin (TetHc) were used as vaccines in a mouse model of melioidosis. The level of protection provided by deacetylated CPS was significantly lower than that from native, acetylated CPS. In addition, sera from mice vaccinated with the deacetylated CPS conjugate did not recognise native CPS. This suggests that CPS extracted from B. thailandensis can be used as antigen and that the acetyl group is essential for protection.
      Graphical abstract image

      PubDate: 2017-09-26T13:45:26Z
       
  • Base-modified GDP-mannose derivatives and their substrate activity towards
           a yeast mannosyltransferase
    • Abstract: Publication date: Available online 21 September 2017
      Source:Carbohydrate Research
      Author(s): Alice Collier, Gerd K. Wagner
      We have previously developed a new class of inhibitors and chemical probes for glycosyltransferases through base-modification of the sugar-nucleotide donor. The key feature of these donor analogues is the presence of an additional substituent at the nucleobase. To date, the application of this general concept has been limited to UDP-sugars and UDP-sugar-dependent glycosyltransferases. Herein, we report for the first time the application of our approach to a GDP-mannose-dependent mannosyltransferase. We have prepared four GDP-mannose derivatives with an additional substituent at either position 6 or 8 of the nucleobase. These donor analogues were recognised as donor substrates by the mannosyltransferase Kre2p from yeast, albeit with significantly lower turnover rates than the natural donor GDP-mannose. The presence of the additional substituent also redirected enzyme activity from glycosyl transfer to donor hydrolysis. Taken together, our results suggest that modification of the donor nucleobase is, in principle, a viable strategy for probe and inhibitor development against GDP-mannose-dependent GTs.
      Graphical abstract image

      PubDate: 2017-09-26T13:45:26Z
       
  • The convergent synthesis and anticancer activity of broussonetinines
           related analogues
    • Abstract: Publication date: Available online 19 September 2017
      Source:Carbohydrate Research
      Author(s): Dominika Jacková, Miroslava Martinková, Jozef Gonda, Kvetoslava Stanková, Martina Bago Pilátová, Peter Herich, Jozef Kožíšek
      The convergent synthesis of broussonetinines related congeners 3 and 4 with the simple C13 alkyl side chain and differently configured pyrrolidine skeleton has been achieved. Our approach relied on the [3,3]-sigmatropic rearrangements of chiral allylic substrates derived from d-xylose. Cross metathesis of the common oxazolidinone intermediates 7 and 8 with tridec-1-ene followed by alkylative cyclization completed the construction of both C-alkyl iminosugars. The targeted compounds 3 and 4 were screened for antiproliferative/cytotoxic activities against multiple cancer cell lines by MTT assay. Compound 3 exhibited very good in vitro potency on Caco-2 and Jurkat cell lines with IC50 value of 5.1 μM and 5.8 μM, respectively.
      Graphical abstract image

      PubDate: 2017-09-26T13:45:26Z
       
  • Graphical contents list
    • Abstract: Publication date: 10 October 2017
      Source:Carbohydrate Research, Volume 450


      PubDate: 2017-09-19T19:38:50Z
       
  • Limitations in the description of conformational preferences of
           C-disaccharides: The (1 → 3)-C-mannobiose case
    • Abstract: Publication date: Available online 18 September 2017
      Source:Carbohydrate Research
      Author(s): Ivan Raich, Zuzana Lövyová, Ladislav Trnka, Kamil Parkan, Jiří Kessler, Radek Pohl, Jakub Kaminský
      Conformational preferences of two C-glycosyl analogues of Manp-(1 → 3)-Manp, were studied using a combined method of theoretical and experimental chemistry. Molecular dynamics was utilized to provide conformational behavior along C-glycosidic bonds of methyl 3-deoxy-3-C-[(α-d-mannopyranosyl)methyl]-α-d- and l-mannopyranosides. The OPLS2005 and Glycam06 force fields were used. Simulations were performed with explicit water (TIP3P) and methanol. Results were compared with a complete conformational scan at the MM4 level with the dielectric constant corresponding to methanol. In order to verify predicted conformational preferences, vicinal 3 J HH NMR coupling constants were calculated by the Karplus equation on simulated potential energy surfaces (PES). A set of new parameters for the Karplus equation was also designed. Predicted 3 J HH were compared with experimental data. We also used reverse methodology, in which the 3 J HH coupling constants were calculated at the DFT level for each family of (ϕ, ψ)-conformers separately and then experimental values were decomposed onto calculated 3 J HH couplings in order to obtain experimentally derived populations of conformers. As an alternative method of evaluation of preferred conformers, analysis of sensitive 13C chemical shifts was introduced. We were able to thoroughly discuss several fundamental issues in predictions of preferred conformers of C-saccharides, such as the solvent effect, reliability of the force field, character of empirical Karplus equation or applicability of NMR parameters in predictions of conformational preferences in general.
      Graphical abstract image

      PubDate: 2017-09-19T19:38:50Z
       
  • Synthesis of a biotinylated keratan sulfate tetrasaccharide composed of
           dimeric Galβ1-4GlcNAcβ6S
    • Abstract: Publication date: Available online 18 September 2017
      Source:Carbohydrate Research
      Author(s): Naoko Takeda-Okuda, Yoshiki Yamaguchi, Jun Uzawa, Jun-ichi Tamura
      We successfully synthesized the biotinylated keratan sulfate tetrasaccharide, Galβ1-4GlcNAc(6S)β1-3Galβ1-4GlcNAcβ(6S) in a stereocontrolled manner. The suitably protected Galβ1-4GlcNPhth unit was converted to the corresponding donor and acceptor. Optimization in 2 + 2 coupling using AgOTf, CuBr2, and n-Bu4NBr in CH3NO2 at a low temperature afforded the desired tetrasaccharide that suppressed glycal formation. The subsequent chemoselective removal of the protecting group at O-6 of two GlcNAcs, sulfation, and deprotection procedures as well as biotinylation gave the target compound.
      Graphical abstract image

      PubDate: 2017-09-19T19:38:50Z
       
  • Chemoenzymatic synthesis of Neu5Ac9NAc-containing α2–3- and
           α2–6-linked sialosides and their use for sialidase substrate
           specificity studies
    • Abstract: Publication date: Available online 18 September 2017
      Source:Carbohydrate Research
      Author(s): Wanqing Li, An Xiao, Yanhong Li, Hai Yu, Xi Chen
      O-Acetylation of sialic acid (Sia) modulates its recognition by sialic acid-binding proteins and plays an important role in biological and pathological processes. 9-O-Acetylation is the most common modification of sialic acid in human. However, study of O-acetylated sialoglycans is hampered due to the instability of O-acetyl group towards pH changes and sensitivity to esterases. Our previous studies demonstrated a chemical biology method to this problem by replacing the oxygen atom in the C9 ester group of sialic acid by a nitrogen to form an amide. Here, we synthesized a library of sixteen new 9-acetamido-9-deoxy-N-acetylneuraminic acid (Neu5Ac9NAc)-containing α2–3- and α2–6-linked sialosides with various underlying glycans using efficient one-pot three-enzyme (OP3E) sialylation systems. Neu5Ac9NAc-containing compounds with a para-nitrophenol aglycon have been used together with their 9-O-acetyl analogs in microtiter plate-based high-throughput substrate specificity studies of nine different sialidases including those from humans and bacteria. In general, similar to 9-O-acetylation, 9-N-acetyl modification of sialic acid in the substrates lowers sialic acid-cleavage activity of most sialidases. In most cases, Neu5Ac9NAc is a good analog of 9-O-acetyl sialic acid. However, exceptions do exist. For example, 9-N- and 9-O-acetyl modifications have different effects on the sialosides cleave efficiencies of a commercially available C. perfringens sialidase as well as recombinant Streptococcus pneumoniae sialidase SpNanC and Bifidobacterium infantis sialidase BiNanH2. The mechanism for the difference awaits further investigation.
      Graphical abstract image

      PubDate: 2017-09-19T19:38:50Z
       
  • Theoretical study on the anomeric effect in α-substituted
           tetrahydropyrans and piperidines
    • Abstract: Publication date: Available online 15 September 2017
      Source:Carbohydrate Research
      Author(s): Francisco A. Martins, Josué M. Silla, Matheus P. Freitas
      Conformational effects, including some controversial examples, have been reported in this work for 2-substituted tetrahydropyrans and piperidines, and for the respective protonated compounds [substituent = F, OH, OCH3, NH2, NHCH3 and N(CH3)2]. Hyperconjugation plays a major role in most cases, either due to endo or exo-anomeric interactions, especially when nitrogen is the electron donor to an antiperiplanar σ* orbital. This interaction also seems to contribute for the Perlin and reverse fluorine Perlin-like effects, which are related to the relative magnitude of 1 J C,H and 1 J C,F coupling constants, respectively, in axial and equatorial conformers. However, the preference for an equatorial conformation appears when a hydrogen or methyl group of the substituent faces the ring, increasing the steric repulsion, even if concomitant with a hyperconjugative interaction in the axial isomer, such as for the well-known 2-aminotetrahydropyran. Unlike some reports in the literature, the gas phase 2-hydroxypiperidine experiences the herein called reverse anomeric effect, although the highly stabilizing n N → σ*C-O interaction in the axial isomer. Overall, steric effects should be taken into account when deciding for the normal or reverse anomeric effects as determinant factors of the stereochemical control of carbohydrate-like molecules.
      Graphical abstract image

      PubDate: 2017-09-19T19:38:50Z
       
  • Novel teichulosonic acid and glycosyl 1-phosphate polymers from the cell
           walls of Arthrobacter sp., strains VKM Ac-2549 and VKM Ac-2550,
           phylogenetically close to Arthrobacter crystallopoietes
    • Abstract: Publication date: Available online 14 September 2017
      Source:Carbohydrate Research
      Author(s): Natalia V. Potekhina, Nikolay P. Arbatsky, Alexander S. Shashkov, Andrey S. Dmitrenok, Sofya N. Senchenkova, Lubov V. Dorofeeva, Lyudmila I. Evtushenko
      Novel teichulosonic acid with the repeating unit →6)-β-D-GlcpNAc-(1→8)-α-Kdn-(2→ has been found in the cell walls of two Arthrobacter strains, VKM Ac-2549 and VKM Ac-2550. The teichulosonic acid was revealed in representatives of the genus Arthrobacter for the first time. Two other polymers identified in the above strains were poly(monoglycosyl 1-phosphate) and poly(diglycosyl 1-phosphate) of hitherto unknown structures, i.e., -6)-α-D-GalpNAc-(1-P-, and -6)-β-D-GlcpNAc-(1→3)-α-D-Galp-(1-P-. The structures of all three polymers were established by using chemical, NMR spectroscopic and ESI-MS methods. The strains studied in this work differ in the cell wall composition from the type strain of phylogenetically closely related species A. crystallopoietes which was reported to contain a teichoic acid and supposedly had a glycosyl 1-phosphate polymer.
      Graphical abstract image

      PubDate: 2017-09-19T19:38:50Z
       
  • Stereoselective sialylation with O-trifluoroacetylated thiosialosides:
           Hydrogen bonding involved'
    • Abstract: Publication date: Available online 8 September 2017
      Source:Carbohydrate Research
      Author(s): Nikita M. Podvalnyy, Nelly N. Malysheva, Maria V. Panova, Alexander I. Zinin, Alexander O. Chizhov, Anna V. Orlova, Leonid O. Kononov
      A series of novel sialyl donors containing O-trifluoroacetyl (TFA) groups at various positions was synthesized. The choice of protecting groups in sialyl donors was based on hypothesis that variations in ability of different acyl groups to act as hydrogen bond acceptors would influence the supramolecular structure of reaction mixture (solution structure), hence the outcome of sialylation. These glycosyl donors were examined in the model glycosylation of the primary hydroxyl group of 1,2:3,4-di-O-isopropylidene-α-D-galactopyranose in comparison with sialyl donors without O-TFA groups. The presence of O-TFA groups in a sialyl donor strongly affected the outcome of sialylation. Several sialyl donors studied showed promising results: yields of disaccharides can be as high as 86% as can be the stereoselectivities (α/β up to 15:1). The results obtained suggest that varying acyl O-protecting groups in sialyl donor may result in dramatic changes in the outcome of sialylation although further studies are required to dissect the influence of intermolecular hydrogen bonding and intramolecular substituent effects related to variations of electron-withdrawing properties of different acyl groups.
      Graphical abstract image

      PubDate: 2017-09-13T21:20:04Z
       
  • Synthesis of a trisaccharide repeating unit of the O-antigen from
           Burkholderia cenocepacia and its dimer
    • Abstract: Publication date: Available online 8 September 2017
      Source:Carbohydrate Research
      Author(s): Ningning Bi, Chenghe Xiong, Guoxia Jin, Zhongwu Guo, Guofeng Gu
      The trisaccharide repeating unit of an O-antigen derived from Burkholderia cenocepacia and its dimer, i.e., α-L-Rhap-(1 → 3)-α-D-GalpNAc-(1 → 3)-β-D-GalpNAc-O(CH2)3N3 (1) and α-L- Rhap-(1 → 3)-α-D-GalpNAc-(1 → 3)-β-D-GalpNAc-(1 → 4)-α-L-Rhap-(1 → 3)-α-D-GalpNAc-(1 → 3)-β-D-GalpNAc-O(CH2)3N3 (2), respectively, were synthesized via a highly convergent strategy. Glycosylation of galactosaminyl acceptor 4 with galactosaminyl trichloroacetimidate donor 5 was followed by condensation of resulting disaccharide acceptor 12 with rhamnosyl imidate donor 6 to furnish stereoselectively trisaccharyl thioglycoside 3, which was used as a key and common glycosyl donor for the construction of both 1 and 2. Title molecule 1 was prepared by glycosylation of 3-azidopropanol with 3 and subsequently global deprotection, whereas coupling reaction of 3 with a trisaccharide acceptor 21 containing an 2,3-O-position acetonide-modified rhamnose residue, followed by global deprotection, generated the dimer 2 in a convergent [3 + 3] manner.
      Graphical abstract image

      PubDate: 2017-09-13T21:20:04Z
       
  • One-pot synthesis of oxazolidine-2-thione and thiozolidine-2-thione from
           sugar azido-alcohols
    • Abstract: Publication date: 10 October 2017
      Source:Carbohydrate Research, Volume 450
      Author(s): Kunj B. Mishra, Anand K. Agrahari, Vinod K. Tiwari
      A controlled and facile synthesis of various glycosyl 1,3-oxazolidine-2-thiones and 1,3- thiozolidine-2-thiones has been accomplished from corresponding sugar azido alcohols utilizing Staudinger reaction (PPh3 and CS2) via isothiocynate route. A series of reactions were performed to investigate the effects of CS2 and PPh3 on the selectivity of product formed. The excessive addition of CS2 with PPh3(1.2 equiv) afforded oxazolidine-2-thione alone, while the solitary addition of PPh3 for 30 min followed by addition of CS2 to the reaction mixture resulted both the products in different ratios, which were successfully isolated using column chromatography (SiO2). Furthermore, synthesis of 1,3-oxathiolan-2-imine from glycosyl epoxide has also been attempted. Structures of all the developed compounds have been elucidated using extensive spectroscopic techniques including IR, NMR and MS analysis.
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      PubDate: 2017-09-02T10:17:22Z
       
  • A carbon tetrachloride-free synthesis of N-phenyltrifluoroacetimidoyl
           chloride
    • Abstract: Publication date: 10 October 2017
      Source:Carbohydrate Research, Volume 450
      Author(s): Dylan G.M. Smith, Spencer J. Williams
      N-Phenyltrifluoroacetimidoyl chloride (PTFAI-Cl) is a reagent widely used for the preparation of glycosyl N-phenyltrifluoroacetimidates. However, the most commonly applied method requires carbon tetrachloride, a hepatotoxic reagent that has been phased out under the Montreal Protocol. We report a new synthesis of N-phenyltrifluoroacetimidoyl chloride (PTFAI-Cl) using dichlorotriphenylphosphane and triethylamine.
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      PubDate: 2017-09-02T10:17:22Z
       
  • Chemical synthesis of guanosine diphosphate mannuronic acid (GDP-ManA) and
           its C-4-O-methyl and C-4-deoxy congeners
    • Abstract: Publication date: 10 October 2017
      Source:Carbohydrate Research, Volume 450
      Author(s): Qingju Zhang, P.Lynne Howell, Herman S. Overkleeft, Dmitri V. Filippov, Gijsbert A. van der Marel, Jeroen D.C. Codée
      Described is the first synthesis of guanosine diphosphate mannuronic acid (GDP-ManA), the sugar donor used by algae and bacteria for the production of alginate, an anionic polysaccharide composed of β-d-mannuronic acid (ManA) and α-l-guluronic acid (GulA). Understanding the biosynthesis of these polyanionic polysaccharides on the molecular level, opens up avenues to use and modulate the biosynthesis machinery for biotechnological and therapeutic applications. The synthesis reported here delivers multi-milligram amounts of the GDP-ManA donor that can be used to study the polymerase (Alg8 in Pseudomonas aeruginosa) that generates the poly-ManA chain. Also reported is the assembly of two close analogues of GDP-ManA: the first bears a C-4-O-methyl group, while the second has been deoxygenated at this position. Both molecules may be used as “chain stoppers” in future enzymatic ManA polymerisation reactions. The crucial pyrophosphate linkage of the GDP-mannuronic acids has been constructed by the phosphorylation of the appropriate ManA-1-phosphates with a guanosine phosphoramidite.
      Graphical abstract image

      PubDate: 2017-09-02T10:17:22Z
       
  • Synthesis of a model trisaccharide for studying the interplay between the
           anti α-Gal antibody and the trans-sialidase reactions in Trypanosoma
           cruzi
    • Abstract: Publication date: 10 October 2017
      Source:Carbohydrate Research, Volume 450
      Author(s): M. Eugenia Giorgi, Rosana Lopez, Rosalia Agusti, Carla Marino, Rosa M. de Lederkremer
      Trypanosoma cruzi, the etiologic agent of Chagas disease, is covered by a dense glycocalix mainly composed by glycoproteins called mucins which are also the acceptors of sialic acid in a reaction catalyzed by a trans-sialidase (TcTS). Sialylation of trypomastigote mucins protects the parasite from lysis by the anti α-Galp antibodies from serum. The TcTS is essential for the infection process since T. cruzi is unable to biosynthesize sialic acid. The enzyme specifically transfers it from a terminal β-d-Galp unit in the host glycoconjugate to terminal β-d-Galp units in the parasite mucins to construct the d-NeuNAc(α2→3)β-d-Galp motif. On the other hand, although galactose is the most abundant sugar in mucins of both, the infective trypomastigotes and the insect stage epimastigotes, α-d-Galp is only present in the infective stage whereas β-d-Galf is characteristic of the epimastigote stage of the less virulent strains. Neither α-d-Galp nor d-Galf is acceptor of sialic acid. In the mucins, some of the oligosaccharides are branched with terminal β-d-Galp units to be able to accept sialic acid in the TcTS reaction. Based on previous reports showing that anti α-Galp antibodies only partially colocalize with sialic acid, we have undertaken the synthesis of the trisaccharide α-d-Galp(1→3)-[β-d-Galp(1→6)]-d-Galp, the smallest structure containing both, the antigenic d-Galp(α1→3)-d-Galp unit and the sialic acid-acceptor β-d-Galp unit. The trisaccharide was obtained as the 6-aminohexyl glycoside to facilitate further conjugation for biochemical studies. The synthetic approach involved the α-galactosylation at O-4 of a suitable precursor of the reducing end, followed by β-galactosylation at O-6 of the same precursor and introduction of the 6-aminohexyl aglycone. The fully deprotected trisaccharide was successfully sialylated by TcTS using either 3′-sialyllactose or fetuin as donors. The product, 6-aminohexyl α-d-NeuNAc(2→3)-β-d-Galp(1→6)-[α-d-Galp(1→3)]-β-d-Galp, was purified and characterized.
      Graphical abstract image

      PubDate: 2017-09-02T10:17:22Z
       
  • Alternate synthesis to d-glycero-β-d-manno-heptose 1,7-biphosphate
    • Abstract: Publication date: 10 October 2017
      Source:Carbohydrate Research, Volume 450
      Author(s): Janelle Sauvageau, Milan Bhasin, Cynthia X. Guo, Itunuoluwa A. Adekoya, Scott D. Gray-Owen, Stefan Oscarson, Lorenzo Guazzelli, Andrew Cox
      d-glycero-β-d-manno-heptose 1,7-biphosphate (HBP) is an enzymatic intermediate in the biosynthesis of the heptose component of lipopolysaccharide (LPS), and was recently revealed to be a pathogen-associated molecular pattern (PAMP) that allows detection of Gram-negative bacteria by the mammalian immune system. Cellular detection of HBP depends upon its stimulation of a cascade that leads to the phosphorylation and assembly of the TRAF-interacting with forkhead-associated domain protein A (TIFA), which activates the transcription factor NF-κB. In this note, an alternate chemical synthesis of HBP is described and its biological activity is established, providing pure material for further assessing and exploiting the biological activity of this compound.
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      PubDate: 2017-09-02T10:17:22Z
       
  • Genetic and structural elucidation of capsular polysaccharides from
           Streptococcus pneumoniae serotype 23A and 23B, and comparison to serotype
           23F
    • Abstract: Publication date: 10 October 2017
      Source:Carbohydrate Research, Volume 450
      Author(s): Neil Ravenscroft, Aneesa Omar, Jason Hlozek, Cesarina Edmonds-Smith, Rainer Follador, Fabio Serventi, Gerd Lipowsky, Michelle M. Kuttel, Paola Cescutti, Amirreza Faridmoayer
      Streptococcus pneumoniae is a globally important encapsulated human pathogen with approximately 100 different serotypes recognized. Serogroup 23 consists of serotype 23F, present in licensed vaccines, and emerging serotypes 23A and 23B. Here, we report the previously unknown structures of the pneumococcal capsular polysaccharides serotype 23A and 23B determined using genetic analysis, NMR spectroscopy, composition and linkage analysis and Smith degradation (of polysaccharide 23A). The structure of the serotype 23A capsular polysaccharide is: →4)-β-D-Glcp-(1→3)-[[α-L-Rhap-(1→2)]-[Gro-(2→P→3)]-β-D-Galp-(1→4)]-β-L-Rhap-(1→. This structure differs from polysaccharide 23F as it features a disaccharide backbone and the di-substituted β-Gal is linked to β-Rha as a side chain. This is due to the different polymerization position catalysed by the unusually divergent repeat unit polymerase Wzy in the 23A cps biosynthesis locus. Steric crowding in 23A, confirmed by molecular models, causes the NMR signal for H-1 of the di-substituted 2,3-β-Gal to resonate in the α-anomeric region. The structure of the serotype 23B capsular polysaccharide is the same as 23F, but without the terminal α-Rha: →4)-β-D-Glcp-(1→4)-[Gro-(2→P→3)]-β-D-Galp-(1→4)-β-L-Rhap-(1→. The immunodominant terminal α-Rha of 23F is more sterically crowded in 23A and absent in 23B. This may explain the reported typing cross reactions for serotype 23F: slight with 23A and none with 23B.
      Graphical abstract image

      PubDate: 2017-09-02T10:17:22Z
       
  • Graphical contents list
    • Abstract: Publication date: 8 September 2017
      Source:Carbohydrate Research, Volume 449


      PubDate: 2017-09-02T10:17:22Z
       
  • Glycoconjugate probes containing a core-fucosylated N-glycan trisaccharide
           for fucose lectin identification and purification
    • Abstract: Publication date: 8 September 2017
      Source:Carbohydrate Research, Volume 449
      Author(s): Deqin Cai, Chaochao Xun, Feng Tang, Xiaobo Tian, Liyun Yang, Kan Ding, Wenzhe Li, Zhiping Le, Wei Huang
      Glyco-PAMAM dendrimers and glyco-agarose beads bearing a core-fucosylated N-glycan trisaccharide GlcNAcβ1,4(Fucα1,6)GlcNAc or a non-fucose disaccharide GlcNAcβ1,4GlcNAc were successfully synthesized and characterized by monosaccharide analysis with HPAEC-PAD technique. These glycoconjugates as fucose lectin probes were applied in fucose-specific lectin detection and purification. The model fucose lectin AAL indicated binding activity with the FITC-labeled PAMAM carrying core-fucose trisaccharide. An affinity chromatography column stuffed with the agarose beads carrying core-fucosylated trisaccharide exhibited a good specificity in purification of AAL than non-fucose disaccharide agarose beads. These novel glycoconjugates bearing the precise and simplified core-fucose N-glycan structure provided a potential application for core-fucose-specific lectin discovery.
      Graphical abstract image

      PubDate: 2017-09-02T10:17:22Z
       
  • Erylosides F8, V1–V3, and W–W2 – New triterpene oligoglycosides from
           the Carribean sponge Erylus goffrilleri
    • Abstract: Publication date: 8 September 2017
      Source:Carbohydrate Research, Volume 449
      Author(s): Alexandr S. Antonov, Anatoly I. Kalinovsky, Shamil S. Afiyatullov, Elena V. Leshchenko, Pavel S. Dmitrenok, Ekaterina A. Yurchenko, Vladimir I. Kalinin, Valentin A. Stonik
      Seven new triterpene glycosides, erylosides F8 (1), V1 (2), V2 (3), V3 (4), W (5), W1 (6) and W2 (7), were isolated from a Carribean sponge Erylus goffrilleri collected from the Carribean Sea near the Arrecife-Seco reef (Cuba). Structures of the glycosides were determined using 1H and 13C NMR spectroscopy, including 2D NMR procedures (1H–1H COSY, 1H–13С HMBC, 1H–13С HSQC and NOESY) and HR ESI mass spectrometry. Erylosides 1 and 4 have 14-carboxy-24,25-dimethyllanost-8(9)-en-3β,25-diol as aglycone whereas glycosides 2, 3, 5, 6 and 7 are 14-carboxy-24-acetoxy-24-methyllanost-8(9)-en-3β-ol glycoconjugates. Cytotoxic activities of the isolated compounds against Ehrlich carcinoma cells and hemolysis were examined and their dependence on eryloside structure was evaluated.
      Graphical abstract image

      PubDate: 2017-09-02T10:17:22Z
       
  • Characteristic oligosaccharides released from acid hydrolysis for the
           structural analysis of chondroitin sulfate
    • Abstract: Publication date: 8 September 2017
      Source:Carbohydrate Research, Volume 449
      Author(s): Jiaojiao Lu, Chunqing Ai, Li Guo, Yinghuan Fu, Chunyang Cao, Shuang Song
      Because the glycosidic linkage of uronic acid is most resistant to acid, oligosaccharides may be formed during the acid hydrolysis of acidic polysaccharides. To take chondroitin sulfate (CS) as an example of acidic polysaccharides, the present study characterized the oligosaccharides released through acid hydrolysis and demonstrated their usefulness for structural confirmation. Acid hydrolysates of commercial standard CSs from shark cartilage and porcine bone were elucidated using HPLC-MSn after 1-phenyl-3-methyl-5-pyrazolone (PMP) derivatization, and altogether 11 di-, tri- and tetra-saccharides with or without sulfate/acetyl groups were identified by their multi-stage mass spectra. Meanwhile the trends of reaction yields of these oligosaccharides alone with trifluoroacetic acid (TFA) concentrations (0.1–2.0 M) were investigated, and 0.2 M TFA was recommended. Then three real samples, sturgeon backbone, porcine trachea and sea cucumber were analyzed, and their CSs were identified by detection of characteristic oligosaccharide fragments. The present study indicated that acid hydrolysis could provide information for acetyl substitution, sulfation and glycosidic linkages, and was helpful for the structural analysis of acidic polysaccharides.
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      PubDate: 2017-09-02T10:17:22Z
       
  • Pyruvylated cell wall glycopolymers of Promicromonospora citrea VKM
           A≿-665T and Promicromonospora sp. VKM A≿-1028
    • Abstract: Publication date: 8 September 2017
      Source:Carbohydrate Research, Volume 449
      Author(s): Andrey S. Dmitrenok, Galina M. Streshinskaya, Elena M. Tul'skaya, Natalia V. Potekhina, Sof'ya N. Senchenkova, Alexander S. Shashkov, Maria I. Bilan, Irina P. Starodumova, Olga V. Bueva, Lyudmila I. Evtushenko
      The cell walls of two strains of the genus Promicromonospora (phylum Actinobacteria) were found to include non-phosphorylated anionic glycopolymers with pyruvic acid acetals of R-configuration. The cell wall of the type strain P. citrea 665T contains two glycopolymers of the sort, including the Kdn-teichulosonic acid with the repeating unit →6)-α-d-Gl≿p/→6)-α-d-Gl≿p3SO3 −-(1 → 4)-α-[7,9Pyr]-Kdn-(2→, and the galactan with the repeating unit →3)-α-[4,6Pyr]-d-Galp-2OAc-(1 → . The cell wall of Promicromonospora sp.VKM Ac-1028 contains the teichuronic acid with the repeating unit →6)-α-d-Gl≿p-(1 → 4)-β-[2,3Pyr]-d-GlcpA-(1 → . The detected glycopolymer structures are reported for the first time. Presented results expand the notion on the diversity of the organic world and on the role of the structures and composition of cell wall polymers in bacterial taxonomy. The glycopolymer structures were established by using a combination of chemical methods, NMR- and IR-spectroscopy, and ESI MS.
      Graphical abstract image

      PubDate: 2017-09-02T10:17:22Z
       
  • Enzymatic synthesis of ribo- and 2′-deoxyribonucleosides from
           glycofuranosyl phosphates: An approach to facilitate isotopic labeling
    • Abstract: Publication date: 8 September 2017
      Source:Carbohydrate Research, Volume 449
      Author(s): Wenhui Zhang, Toby Turney, Ivana Surjancev, Anthony S. Serianni
      Milligram quantities of α-D-ribofuranosyl 1-phosphate (sodium salt) (αR1P) were prepared by the phosphorolysis of inosine, catalyzed by purine nucleoside phosphorylase (PNPase). The αR1P was isolated by chromatography in >95% purity and characterized by 1H and 13C NMR spectroscopy. Aqueous solutions of αR1P were stable at pH 6.4 and 4 °C for several months. The isolated αR1P was N-glycosylated with different nitrogen bases (adenine, guanine and uracil) using PNPase or uridine phosphorylase (UPase) to give the corresponding ribonucleosides in high yield based on the glycosyl phosphate. This methodology is attractive for the preparation of stable isotopically labeled ribo- and 2′-deoxyribonucleosides because of the ease of product purification and convenient use and recycling of nitrogen bases. The approach eliminates the need for separate reactions to prepare individual furanose-labeled ribonucleosides, since only one ribonucleoside (inosine) needs to be labeled, if desired, in the furanose ring, the latter achieved by a high-yield chemical N-glycosylation. 2′-Deoxyribonucleosides were prepared from 2′-deoxyinosine using the same methodology with minor modifications.
      Graphical abstract image

      PubDate: 2017-09-02T10:17:22Z
       
  • Recent advances in the chemical synthesis of sugar-nucleotides
    • Abstract: Publication date: Available online 1 September 2017
      Source:Carbohydrate Research
      Author(s): Sanaz Ahmadipour, Gavin J. Miller
      Graphical abstract image

      PubDate: 2017-09-02T10:17:22Z
       
  • Synthesis of a series of new glycoclusters and the evaluation of their
           anti-adhesion activities
    • Abstract: Publication date: Available online 1 September 2017
      Source:Carbohydrate Research
      Author(s): Xiaorong Zhang, Aqin Liu, Zhihui Zhao, Zhongjun Li, Qing Li
      According to our early researches, some glycoclusters having glucose, mannose, cellose and lactose residues showed good anti-adhesion activity of leukocytes to endothelial cells and exerted anti-inflammatory effects. Based on these results and combination principles of drugs, a series of new glycoclusters modifying with potentially anti-oxidant activity pharmacophores have been synthesized, and their anti-adhesion activities were assessed by static state cell-based adhesion assay. The results showed that some modified glycoclusters displayed better activities than their leading compound.
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      PubDate: 2017-09-02T10:17:22Z
       
  • An acceptor analogue of β-1,4-galactosyltransferase: Substrate,
           inhibitor, or both'
    • Abstract: Publication date: Available online 31 August 2017
      Source:Carbohydrate Research
      Author(s): Jingqian Jiang, Gerd K. Wagner
      Many glycosyltransferase inhibitors in the literature are structurally derived from the donor or acceptor substrate of the respective enzyme. A representative example is 2-naphthyl β-d-GlcNAc, a synthetic GlcNAc glycoside that has been reported as a galactosyltransferase inhibitor. This GlcNAc derivative is attractive as a chemical tool compound for biological and biochemical studies because of its reported potency as an inhibitor, and its short and straightforward synthesis from readily available starting materials. We report that in our hands, 2-naphthyl β-d-GlcNAc behaved, unexpectedly, as an acceptor substrate of the inverting β-1,4-galactosyltransferase (β-1,4-GalT) from bovine milk. This substrate activity has not previously been described. We found that 2-naphthyl β-d-GlcNAc can be an acceptor substrate both for recombinantly expressed β-1,4-GalT, and for a commercial batch of the same enzyme, and both in the presence and absence of bovine serum albumin (BSA). As expected for a full acceptor substrate, this substrate activity was time- and concentration-dependent. Additional experiments show that the observed inhibitor/substrate switch is facilitated by a phosphatase that is an essential component of our enzyme-coupled glycosyltransferase assay. These findings suggest that the behaviour of 2-naphthyl β-d-GlcNAc and related acceptor-based glycosyltransferase inhibitors is strongly dependent on the individual assay conditions. Our results therefore have important implications for the use of 2-naphthyl β-d-GlcNAc and related glycosides as tool compounds in glycobiology and glycobiochemistry.
      Graphical abstract image

      PubDate: 2017-09-02T10:17:22Z
       
  • Rational optimization of the mannoside building block for automated
           electrochemical assembly of the core trisaccharide of GPI anchor
           oligosaccharides
    • Abstract: Publication date: Available online 25 August 2017
      Source:Carbohydrate Research
      Author(s): Sujit Manmode, Takumi Sato, Norihiko Sasaki, Ikumi Notsu, Shuichi Hayase, Toshiki Nokami, Toshiyuki Itoh
      We have developed a carbohydrate building block of mannosides based on DFT calculations, electrochemical analysis, and automated solution-phase synthesis. The optimized building block in hand was used to prepare the core trisaccharide of GPI anchor oligosaccharides.
      Graphical abstract image

      PubDate: 2017-09-02T10:17:22Z
       
  • Highly efficient synthesis of bioactive oleanane-type saponins
    • Abstract: Publication date: Available online 23 August 2017
      Source:Carbohydrate Research
      Author(s): Jing-Jing Sui, Wen-Hui Zhou, De-Yong Liu, Ming-Qing Li, Jian-Song Sun
      Leveraging on Schmidt glycosylation method, a highly efficient approach to obtain oleanane-type triterpene saponins was fixed, whereby oleanyl mono-, disaccharide (guaianin N), trisaccharide (elatoside E), as well as tetrasaccharide (elatoside F) were obtained efficiently. The synthetic investigation has resulted in the discovery of the effect of branch-sugar incorporation sequence on the overall synthetic efficiency. Moreover, through bioactivity investigation, the cytotoxic activity of the obtained triterpenoid saponins was evaluated, and the preliminary structure-activity relationship was deduced.
      Graphical abstract image

      PubDate: 2017-09-02T10:17:22Z
       
  • The trehalose-specific transporter LpqY-SugABC is required for
           antimicrobial and anti-biofilm activity of trehalose analogues in
           Mycobacterium smegmatis
    • Abstract: Publication date: Available online 9 August 2017
      Source:Carbohydrate Research
      Author(s): Jeffrey M. Wolber, Bailey L. Urbanek, Lisa M. Meints, Brent F. Piligian, Irene C. Lopez-Casillas, Kailey M. Zochowski, Peter J. Woodruff, Benjamin M. Swarts
      Mycobacteria, including the bacterial pathogen that causes human tuberculosis, possess distinctive pathways for synthesizing and utilizing the non-mammalian disaccharide trehalose. Trehalose metabolism is essential for mycobacterial viability and has been linked to in vitro biofilm formation, which may bear relevance to in vivo drug tolerance. Previous research has shown that some trehalose analogues bearing modifications at the 6-position inhibit growth of various mycobacterial species. In this work, 2-, 5-, and 6-position-modified trehalose analogues were synthesized using our previously reported one-step chemoenzymatic method and shown to inhibit growth and biofilm formation in the two-to three-digit micromolar range in Mycobacterium smegmatis. The trehalose-specific ABC transporter LpqY-SugABC was essential for antimicrobial and anti-biofilm activity, suggesting that inhibition by monosubstituted trehalose analogues requires cellular uptake and does not proceed via direct action on extracellular targets such as antigen 85 acyltransferases or trehalose dimycolate hydrolase. Although the potency of the described compounds in in vitro growth and biofilm assays is moderate, this study reports the first carbohydrate-based mycobacterial biofilm inhibitors and reinforces the concept of exploiting unique sugar uptake pathways to deliver inhibitors and other chemical cargo to mycobacteria.
      Graphical abstract image

      PubDate: 2017-09-02T10:17:22Z
       
  • Tunable stereoselectivity in the synthesis of α- and β-aryl glycosides
           using 1,2-α-anhydrosugars as glycosyl donors
    • Abstract: Publication date: 8 September 2017
      Source:Carbohydrate Research, Volume 449
      Author(s): Devaraj Somasundaram, Kalpattu K. Balasubramanian, Shanmugasundaram Bhagavathy
      The stereochemical course of O-glycosidation of 1,2-α -d-anhydrosugars (glycal epoxides) with phenols can be tuned by varying the metal ion of the base. While the reaction of 1,2-α -d-anhydrosugars with phenols mediated by trimethylaluminium leads exclusively to 1,2-cis-α-O-aryl glycosides, similar reaction mediated by caesium carbonate gives exclusively 1,2-trans-β-O-aryl glycosides. In contrast, reaction with phenoxides generated from Grignard reagent and calcium salts affords mixture of the anomers.
      Graphical abstract image

      PubDate: 2017-08-02T11:27:21Z
       
  • Physakengoses K-Q, seven new sucrose esters from Physalis alkekengi var.
           franchetii
    • Abstract: Publication date: Available online 28 July 2017
      Source:Carbohydrate Research
      Author(s): Chuan-Yang Zhang, Jian-Guang Luo, Rui-Huan Liu, Ru Lin, Ming-Hua Yang, Ling-Yi Kong
      Seven sucrose esters, physakengoses K-Q (1–7) were isolated from the aerial parts of Physalis alkekengi var. franchetii. Their structures were elucidated on the basis of extensive spectroscopic analyses and chemical methods. These new compounds were tested for their antimicrobial abilities against Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa and Escherichia coli. Among the isolated sucrose esters, compounds 1–5 showed potent antibacterial activity with MIC values ranging from 2.16 to 12.76 μg/mL.
      Graphical abstract image

      PubDate: 2017-08-02T11:27:21Z
       
  • Anti-inflammatory effect of sugar-amino acid Maillard reaction products on
           intestinal inflammation model in vitro and in vivo
    • Abstract: Publication date: 8 September 2017
      Source:Carbohydrate Research, Volume 449
      Author(s): Jun-Gu Oh, Su-Hyun Chun, Da Hyun Kim, Jin Hye Kim, Hye Soo Shin, Yong Soo Cho, Yong Ki Kim, Hee-don Choi, Kwang-Won Lee
      The Maillard reaction is a nonenzymatic reaction between an amino acid and a reducing sugar that usually occurs upon heating. This reaction occurs routinely in cooking, generates numerous products, which are collectively referred to as Maillard reaction products (MRPs) contributing to aroma and color features. Advanced glycation end-products (AGEs) transformed from MRPs are participated in many types of inflammation reaction. In this study, various sugar-amino acid MRPs were prepared from three different amino acids (lysine, arginine, and glycine) and sugars (glucose, fructose, and galactose) for 1 h with heating at 121 °C. Treatment of lipopolysaccharide-stimulated RAW264.7 macrophages with the MRPs decreased nitric oxide (NO) expression compared to control without MRPs treatment. MRPs derived from lysine and galactose (Lys-Gal MRPs) significantly inhibited NO expression. The retentate fraction of Lys-Gal MRPs with cut-off of molecular weight of 3–10 kDa (LGCM) suppressed NO expression more effectively than did Lys-Gal MRPs. The anti-inflammatory effect of LGCM was evaluated using a co-culture system consisting of Caco-2 (apical side) and RAW264.7 or THP-1 (basolateral side) cells to investigate the gut inflammation reaction by stimulated macrophage cells. In this system, LGCM prevented a decreased transepithelial electrical resistance, and decreased both tumor necrosis factor-α production in macrophages and interleukin (IL)-8 and IL-1β mRNA expression in Caco-2 cells. In co-culture and in vivo dextran sulfate sodium (DSS)-induced colitis model study, we also observed the anti-inflammatory activity of LGCM.
      Graphical abstract image

      PubDate: 2017-07-23T08:05:19Z
       
  • A comparative study on the activity of fungal lytic polysaccharide
           monooxygenases for the depolymerization of cellulose in soybean spent
           flakes
    • Abstract: Publication date: Available online 18 July 2017
      Source:Carbohydrate Research
      Author(s): Brian C. Pierce, Jane Wittrup Agger, Zhenghong Zhang, Jesper Wichmann, Anne S. Meyer
      Lytic polysaccharide monooxygenases (LPMOs) are copper-dependent enzymes capable of the oxidative breakdown of polysaccharides. They are of industrial interest due to their ability to enhance the enzymatic depolymerization of recalcitrant substrates by glycoside hydrolases. In this paper, twenty-four lytic polysaccharide monooxygenases (LPMOs) expressed in Trichoderma reesei were evaluated for their ability to oxidize the complex polysaccharides in soybean spent flakes, an abundant and industrially relevant substrate. TrCel61A, a soy-polysaccharide-active AA9 LPMO from T. reesei, was used as a benchmark in this evaluation. In total, seven LPMOs demonstrated activity on pretreated soy spent flakes, with the products from enzymatic treatments evaluated using mass spectrometry and high performance anion exchange chromatography. The hydrolytic boosting effect of the top-performing enzymes was evaluated in combination with endoglucanase and beta-glucosidase. Two enzymes (TrCel61A and Aspte6) showed the ability to release more than 36% of the pretreated soy spent flake glucose – a greater than 75% increase over the same treatment without LPMO addition.
      Graphical abstract image

      PubDate: 2017-07-23T08:05:19Z
       
  • Characterization of the O-antigen polysaccharide derived from Pantoea
           agglomerans IG1 lipopolysaccharide
    • Abstract: Publication date: 8 September 2017
      Source:Carbohydrate Research, Volume 449
      Author(s): Masahito Hashimoto, Rune Satou, Mami Ozono, Hiroyuki Inagawa, Gen-Ichiro Soma
      A polysaccharide fraction was isolated from the Pantoea agglomerans IG1 lipopolysaccharide (IP-PA1), and its O-antigenic polysaccharide was characterized by chemical analyses and 1D and 2D 1H and 13C NMR spectroscopy. The polysaccharide is composed of linear tetrasaccharide repeating units, consisting of glucose and rhamnose, where 40% of one of the rhamnose residues is substituted with glucose: →2)-α-l-Rhap-(1→6)-α-d-Glcp-(1→2)-[β-d-Glcp-(1→3)]0.4-α-l-Rhap-(1→2)-α-l-Rhap-(1→
      Graphical abstract image

      PubDate: 2017-07-09T04:05:05Z
       
  • Structural characterization of glucosylated lactose derivatives
           synthesized by the Lactobacillus reuteri GtfA and Gtf180 glucansucrase
           enzymes
    • Abstract: Publication date: Available online 8 July 2017
      Source:Carbohydrate Research
      Author(s): Hien T.T. Pham, Lubbert Dijkhuizen, Sander S. van Leeuwen
      Glucansucrase enzymes from lactic acid bacteria are receiving strong interest because of their wide range of gluco-oligosaccharide and polysaccharide products from sucrose, some of which have prebiotic potential. Glucansucrases GtfA and Gtf180 from Lactobacillus reuteri strains are known to convert sucrose into α-glucans with different types of linkages, but also to use other molecules as acceptor substrates. Here we report that incubation of (N-terminally truncated versions of) these enzymes with lactose plus sucrose resulted in synthesis of at least 5 glucosylated lactose products of a degree of polymerization (DP) of 3–4. Only glucansucrase Gtf180-ΔN also produced larger lactose-based oligosaccharides (up to DP9). Structural characterization of the glucosylated lactose products DP3-4 revealed glycosidic bonds other than (α1→4)/(α1→6) typical for GtfA-ΔN and (α1→3)/(α1→6) typical for Gtf180-ΔN: Both GtfA-ΔN and Gtf180-ΔN now introduced a glucosyl residue (α1→3)- or (α1→4)-linked to the non-reducing galactose unit of lactose. Both enzymes also were able to introduce a glucosyl residue (α1→2)-linked to the reducing glucose unit of lactose. These lactose derived oligosaccharides potentially are interesting prebiotic compounds.
      Graphical abstract image

      PubDate: 2017-07-09T04:05:05Z
       
  • Evaluation of hydrogen bond networks in cellulose Iβ and II crystals
           using density functional theory and Car–Parrinello molecular dynamics
    • Abstract: Publication date: Available online 5 July 2017
      Source:Carbohydrate Research
      Author(s): Daichi Hayakawa, Yoshiharu Nishiyama, Karim Mazeau, Kazuyoshi Ueda
      Crystal models of cellulose Iβ and II, which contain various hydrogen bonding (HB) networks, were analyzed using density functional theory and Car–Parrinello molecular dynamics (CPMD) simulations. From the CPMD trajectories, the power spectra of the velocity correlation functions of hydroxyl groups involved in hydrogen bonds were calculated. For the Iβ allomorph, HB network A, which is dominant according to the neutron diffraction data, was stable, and the power spectrum represented the essential features of the experimental IR spectra. In contrast, network B, which is a minor structure, was unstable because its hydroxymethyl groups reoriented during the CPMD simulation, yielding a different crystal structure to that determined by experiments. For the II allomorph, a HB network A is proposed based on diffraction data, whereas molecular modeling identifies an alternative network B. Our simulations showed that the interaction energies of the cellulose II (B) model are slightly more favorable than model II(A). However, the evaluation of the free energy should be waited for the accurate determination from the energy point of view. For the IR calculation, cellulose II (B) model reproduces the spectra better than model II (A).
      Graphical abstract image

      PubDate: 2017-07-09T04:05:05Z
       
  • Sulfated polysaccharides of the Vietnamese brown alga Sargassum aquifolium
           (Fucales, Sargassaceae)
    • Abstract: Publication date: Available online 27 June 2017
      Source:Carbohydrate Research
      Author(s): Maria I. Bilan, Nadezhda E. Ustyuzhanina, Alexander S. Shashkov, Thanh Thi Thu Thuy, Bui Minh Ly, Tran Thi Thanh Van, Bui Van Nguyen, Anatolii I. Usov
      A fucoidan preparation named FSA was isolated from the brown alga Sargassum aquifolium collected from the coastal waters of Vietnam. l-Fucose, d-galactose, d-mannose, d-glucuronic acid, d-xylose, and sulfate were found to be the main constituents of FSA. The preparation was fractionated by anion-exchange chromatography on DEAE-Sephacel eluted stepwise with 0.5, 1.0, 1.5, and 2.0 M NaCl to give four fractions differing in monosaccharide composition and degree of sulfation. Their NMR spectra were too complex to be completely interpreted. Fractions 1.0 M and 1.5 M were analyzed by methylation before and after desulfation. In addition, desulfated 1.0 M was fractionated by anion-exchange chromatography into six fractions according to the uronic acid content. They were characterized by methylation and NMR spectral data, and three structurally different polysaccharides were identified. One of them has a core of alternating 2-linked α-d-Manp and 4-linked β-d-GlcpA residues, about a half of the former bearing single α-l-Fucp or β-d-Xylp at position 3. The second polymer is a (1 → 3)-β-d-glucopyranuronan partially substituted with single β-d-Xylp or single α-l-Fucp at position 4. The third polysaccharide is a xylo(fuco)galactan having a linear core of alternating 4-linked α-d-Gal and 3-linked β-d-Gal residues. The latter bear single β-d-Xylp or a short chain of 4-linked β-d-Xyl, 6-linked β-d-Gal, and variously linked α-l-Fuc. In FSA, these polysaccharides are sulfated at different positions and devoid of regularity. Fractions of FSA possess anticoagulant, cytotoxic, and antitumor activities, which increase with the degree of sulfation. The most sulfated fraction 2.0 M that contains mainly a sulfated fucogalactan, is about half as active as anticoagulant as the standard low-molecular mass heparin (enoxaparin).
      Graphical abstract image

      PubDate: 2017-06-28T16:53:23Z
       
  • Gram scale synthesis of A (type 2) and B (type 2) blood group
           tetrasaccharides through 1,6-anhydro-N-acetyl-β-D-glucosamine
    • Abstract: Publication date: Available online 27 June 2017
      Source:Carbohydrate Research
      Author(s): Tatiana V. Tyrtysh, Elena Yu Korchagina, Ivan M. Ryzhov, Nicolai V. Bovin
      Gram scale synthesis of A (type 2) and B (type 2) tetrasaccharides in the form of 3-aminopropyl glycosides is proposed starting from 3-O-benzoyl-1,6-anhydro-N-acetylglucosamine. Its galactosylation followed by re-protection gave lactosamine derivative with single free 2′OH group in total yield 75%. Standard fucosylation and next run of re-protection in total yield 88% gave a trisaccharide Fuc-Gal-anhydroGlcNAc with single free 3′OH group. Its standard α-galactosylation gave protected B (type 2) tetrasaccharide. For synthesis of correspondent A tetrasaccharide seven different 2-azido-2-deoxygalactosyl (GalN3) donors were tested: 6-O-acetyl-3,4-O-isopropylidene-GalN3 thioglycoside was shown to provide the best yield (89%) and stereoselectivity (α/β = 24:1). Further 1,6-anhydro cycle opening, spacer-arming and complete deprotection resulted in the target 3-aminopropyl glycosides of A (type 2) and B (type 2) tetrasaccharides, yields 87 and 85% correspondingly.
      Graphical abstract image

      PubDate: 2017-06-28T16:53:23Z
       
  • Agarose based large molecular systems: Synthesis of fluorescent aromatic
           agarose amino acid nano-conjugates – their pH-stimulated structural
           variations and interactions with BSA
    • Abstract: Publication date: Available online 26 June 2017
      Source:Carbohydrate Research
      Author(s): Atul K. Sharma, Nishith A. Chudasama, Kamalesh Prasad, A.K. Siddhanta
      Two new nano-sized fluorescent 6-amino agarose naphthalic acid half ester derivatives were synthesized (ca.60% yields) employing 1,8- and 2,3-naphthalic acid anhydrides (1,8-AANE, and 2,3-AANE respectively). These large nano molecular frameworks (DLS 3 & 100 nm, and 3 & 152 nm respectively) contains amino, naphthalate half-ester carboxyl groups at the C-6 positions of the 1,3-β-D-galactopyranose moieties of the agarose backbone (overall DS 0.94). Structures were characterized (FT-IR, and 13C & 1H NMR spectrometries). These materials mimicked a large protein conjugate (GPC 123, and 108 kDa) exhibiting pH-responsive conformational variations (optical rotatory dispersion), offering a mixed solubility pattern like a soluble random coil (pH 4–10), and precipitate (pH 2) formation. With bovine serum albumin 1,8- and 2,3-AANE showed complexation, and decomplexation at pH 5.2, and 6.8 respectively. However, they showed decomplexation, and complexation respectively at pH 10 (circular dichroism). These fluorogenic systems may be of prospective utility as chiral sensors and in the realms demanding the virtues of preferential protein bindings.
      Graphical abstract image

      PubDate: 2017-06-28T16:53:23Z
       
  • N-glycan structures of β-HlH subunit of Helix lucorum hemocyanin
    • Abstract: Publication date: Available online 22 June 2017
      Source:Carbohydrate Research
      Author(s): Lyudmila Velkova, Pavlina Dolashka, Jozef Van Beeumen, Bart Devreese
      The carbohydrate structures of molluscan hemocyanins have recently received particular interest due to their specific monosaccharide composition, as well as their immunostimulatory properties and application in clinical studies. For the first time, we investigated N-glycans of the structural subunit β-HlH of hemocyanin isolated from Helix lucorum. In total, 32 different glycans were enzymatically liberated and characterized by tandem mass spectrometry using a Q-Trap mass spectrometer. Our study revealed a highly heterogeneous mixture of glycans with composition Hex3-7HexNAc2-5MeHex0-4Pent0-1Fuc0-1. The oligosaccharide chains are mostly modified at the inner core by β1-2-linked xylose to β-mannose, by α1-6-fucosylation of the innermost GlcNAc residue (the Asn-bound GlcNAc), and by methylation. The glycans of β-HlH mainly contain a terminal MeHex residue; in some cases even two, three or four of these residues occur. Several carbohydrate chains in β-HlH are core-fucosylated without Xyl and also possess a high degree of methylation. This study shows the presence of mono- and bi-antennary N-glycans as well as hybrid type structures with or without core-fucosylation.
      Graphical abstract image

      PubDate: 2017-06-28T16:53:23Z
       
  • Hydrogenolytic cleavage of naphthylmethyl ethers in the presence of
           sulfides
    • Abstract: Publication date: Available online 20 June 2017
      Source:Carbohydrate Research
      Author(s): Philip O. Adero, Dean R. Jarois, David Crich
      With the aid of a series of model thioether or thioglycoside containing polyols protected with combinations of benzyl ethers and 2-naphthylmethyl ethers it is demonstrated that the latter are readily cleaved selectively under hydrogenolytic conditions in the presence of the frequently catalyst-poisoning sulfides. These results suggest the possibility of employing 2-naphthylmethyl ethers in place of benzyl ethers in synthetic schemes when hydrogenolytic deprotection is anticipated in the presence of thioether type functionality.
      Graphical abstract image

      PubDate: 2017-06-21T02:40:05Z
       
  • Structures and gene clusters of the O-antigens of Escherichia albertii O3,
           O4, O6, and O7
    • Abstract: Publication date: Available online 17 June 2017
      Source:Carbohydrate Research
      Author(s): Olesya I. Naumenko, Han Zheng, Sof'ya N. Senchenkova, Hong Wang, Qun Li, Alexander S. Shashkov, Jianping Wang, Yuriy A. Knirel, Yanwen Xiong
      The O-specific polysaccharides (OPSs) called O-antigens were obtained by mild acid degradation of the lipopolysaccharides of Escherichia albertii serotypes O3, O4, O6, and O7 and studied by sugar analysis along with 1D and 2D 1H and 13C NMR spectroscopy. The following structure was established for the OPS of E. albertii O4, which, to our knowledge, is unique among known bacterial polysaccharide structures: →2)-α-l-Rhap-(1 → 2)-α-l-Fucp-(1 → 2)-β-d-Galp-(1 → 3)-α-d-GalpNAc-(1 → 3)-β-d-GlcpNAc-(1→ The OPS structure of the strain of E. albertii O7 studied was identical to that of strain LMG 20973 (= Albert 10457), whose structure has been reported earlier (R. Eserstam et al. Eur. J. Biochem. 269 (2002) 3289–3295). E. albertii O3 and O6 shared the OPS structures with Escherichia coli O181 and O3, respectively, except for the lack of O-acetylation in E. albertii O3, which is present in E. coli O181. The gene clusters driving the O-antigen biosynthesis of the E. albertii strains were sequenced, the genes were annotated by comparison with sequences in the available databases, and the predicted functions of the encoded proteins were found to be consistent with the OPS structures established. In accordance with the relatedness of the OPS structures, the O-antigen gene clusters of E. albertii O3 and O6 contain the same genes and have the same organization as those of E. coli O181 and O3, the entire gene clusters being 83% and 98% identical, respectively.
      Graphical abstract image

      PubDate: 2017-06-21T02:40:05Z
       
 
 
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