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Glucose Unit (glucose + unit)
Selected AbstractsNew Chemical Constituents from Borreria verticillata (Rubiaceae)HELVETICA CHIMICA ACTA, Issue 9 2010Vinicius F. Moreira Abstract A phytochemical study on Borreria verticillata has led to the isolation of two novel simple indole alkaloids, 6-methoxy-4-(3-methylbut-2-en-1-yl)-1H -indole, named verticillatine A (1), and 1-(1H -indol-6-yl)-3-methylbutan-1-one, named verticillatine B (2), one new iridoid, 6,- O -(2-glyceryl)scandoside methyl ester (3), with the glycerol unit linked to a glucose unit, and two known ones, asperuloside (4) and scandoside methyl ester (5). The structures of these compounds were elucidated on the basis of spectroscopic-data analyses, mainly 1H- and 13C-NMR, including 2D experiments (1H,1H-COSY, NOESY, HMBC, and HMQC), and HR-ESI-MS. [source] Synthesis of Half-Channels by the Anionic Polymerization of Ethylene Oxide Initiated by Modified CyclodextrinADVANCED MATERIALS, Issue 40 2009Nezha Badi Amphiphilic star-shaped oligomers are produced by anionic polymerization of ethylene oxide (EO) using per-2,3-di- O -heptyl- , -(or ,)cyclodextrins as initiators , a versatile way of synthesizing artificial channels bearing one polyEO branch per glucose unit. The behavior of the amphiphilic molecules in lipid membranes is studied by electrical measurements, which confirms the formation of transient, well-defined dimeric ionic channels (see figure). [source] Selectivity tuning of cyclodextrin derivatives by specific substitutionJOURNAL OF SEPARATION SCIENCE, JSS, Issue 18 2003Melanie Junge Abstract A new, highly enantioselective cyclodextrin derivative combining the properties of heptakis(6- O - tert -butyldimethylsilyl-2,3-di- O -methyl)-,-cyclodextrin and heptakis(2,3-di- O -acetyl-6- O - tert -butyldimethylsilyl)-,-cyclodextrin was prepared by exchanging a methyl group for an acetyl substituent in a single glucose unit of heptakis(6- O - tert -butyldimethylsilyl-2,3-di- O -methyl)-,-cyclodextrin. A comparative evaluation of the separation capabilities showed that the enantioselectivity of both "parent" cyclodextrin derivatives is transferred to the new chiral stationary phase. [source] Structural characterization and identification of iridoid glycosides, saponins, phenolic acids and flavonoids in Flos Lonicerae Japonicae by a fast liquid chromatography method with diode-array detection and time-of-flight mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 19 2009Lian-Wen Qi A fast liquid chromatography method with diode-array detection (DAD) and time-of-flight mass spectrometry (TOF-MS) has been developed for analysis of constituents in Flos Lonicerae Japonicae (FLJ), a traditional Chinese medicine derived from the flower bud of Lonicerajaponica. The chromatographic analytical time decreased to 25,min without sacrificing resolution using a column packed with 1.8-µm porous particles (4.6,×,50,mm), three times faster than the performance of conventional 5.0-µm columns (4.6,×,150,mm). Four major groups of compounds previously isolated from FLJ were structurally characterized by DAD-TOF-MS: iridoid glycosides showed maximum UV absorption at 240,nm; phenolic acids at 217, 242, and 326,nm; flavonoids at 255 and 355,nm; while saponins had no absorption. In electrospray ionization (ESI)-TOF-MS experiments, elimination of a glucose unit (162 Da), and successive losses of H2O, CH3OH and CO, were generally observed in iridoid glycosides; saponins were characterized by a series of identical aglycone ions; phenolic acids typically generated a base peak at [M,H,caffeoyl], by loss of a caffeic acid unit (162 Da) and several marked quinic acid moiety ions; cleavage of the glycosidic bond (loss of 162 or 308 Da), subsequent losses of H2O, CO, RDA and C-ring fragmentation were the most possible fragmentation pathways for flavonoids. By accurate mass measurements within 4,ppm error for each molecular ion and subsequent fragment ions, as well as the ,full mass spectral' information of TOF-MS, a total of 41 compounds including 13 iridoid glycosides, 11 phenolic acids, 7 saponins, and 10 flavonoids were identified in a methanolic extract of FLJ. Copyright © 2009 John Wiley & Sons, Ltd. [source] Preparation and Characterization of Inclusion Complexes of ,-Cyclodextrin with Ionic LiquidCHEMISTRY - A EUROPEAN JOURNAL, Issue 20 2005Yan-An Gao Abstract The solubilities of ,-cyclodextrin (,-CD), ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF6), and their mixture in water were determined, and the conductivity of these aqueous solutions was measured. It was demonstrated that ,-CD and bmimPF6 could enhance the solubility of each other, and the solubility curves of each were linear with gradients of about 1. The conductivity decreased remarkably with increasing , - CD concentration, and a discernible break in the conductivity curve could be observed when ,-CD and bmimPF6 were equimolar in the solution. The solubility and conductivity results indicated that inclusion complexes (ICs) of 1:1 stoichiometry were formed. The inclusion compounds were further characterized by using powder X-ray diffraction (XRD) analysis, 13C CP/MAS (cross-polarization magic-angle spinning) NMR and 1H NMR spectroscopy, and thermogravimetric analysis (TGA). The results showed that the ICs were a fine crystalline powder. The host,guest system exhibited a channel-type structure and each glucose unit of ,-CD was in a similar environment. The decomposition temperature of the ICs was lower than that of bmimPF6 and ,-CD individually. [source] Molecular determinants of ligand specificity in family 11 carbohydrate binding modules , an NMR, X-ray crystallography and computational chemistry approachFEBS JOURNAL, Issue 10 2008Aldino Viegas The direct conversion of plant cell wall polysaccharides into soluble sugars is one of the most important reactions on earth, and is performed by certain microorganisms such as Clostridium thermocellum (Ct). These organisms produce extracellular multi-subunit complexes (i.e. cellulosomes) comprising a consortium of enzymes, which contain noncatalytic carbohydrate-binding modules (CBM) that increase the activity of the catalytic module. In the present study, we describe a combined approach by X-ray crystallography, NMR and computational chemistry that aimed to gain further insight into the binding mode of different carbohydrates (cellobiose, cellotetraose and cellohexaose) to the binding pocket of the family 11 CBM. The crystal structure of C. thermocellum CBM11 has been resolved to 1.98 Å in the apo form. Since the structure with a bound substrate could not be obtained, computational studies with cellobiose, cellotetraose and cellohexaose were carried out to determine the molecular recognition of glucose polymers by CtCBM11. These studies revealed a specificity area at the CtCBM11 binding cleft, which is lined with several aspartate residues. In addition, a cluster of aromatic residues was found to be important for guiding and packing of the polysaccharide. The binding cleft of CtCBM11 interacts more strongly with the central glucose units of cellotetraose and cellohexaose, mainly through interactions with the sugar units at positions 2 and 6. This model of binding is supported by saturation transfer difference NMR experiments and linebroadening NMR studies. [source] Effect of substrate size on immunoinhibition of amylase activity,JOURNAL OF CLINICAL LABORATORY ANALYSIS, Issue 2 2001Ilka Warshawsky Abstract Immunoinhibition assays are hypothesized to work by antibodies blocking substrate access to enzyme active sites. To test this hypothesis, the inhibition of amylase isoenzymes by monoclonal and polyclonal antisera was assessed using substrates of varying sizes: chromogenic sustrates 3, 5, or 7 glucose units in length, novel synthetic macromolecular substrates, and starch. The synthetic macromolecular substrates consisted of small oligosaccharide substrates linked to an inert polymer that conferred a large size to substrate molecules as determined by gel filtration chromatography. When substrate size increased, amylase activity could be inhibited equivalently by antibody concentrations that are 10‐fold lower. Progressively less polyclonal serum was required to inhibit amylase activity as substrate length increased from 3 to 5 to 7 glucose units and as size was increased by linkage to a polymer. Different effects of substrate size were observed with two monoclonal antibodies. One monoclonal antibody blocked amylase activity independent of substrate size, while another monoclonal antibody had little inhibitory effect except using starch as substrate. We conclude that use of larger substrates can expand the repertoire of inhibitory epitopes on enzymes and convert a noninhibitory antibody into an inhibitory one. J. Clin. Lab. Anal. 15:64–70, 2001. [source] OPTIMIZATION OF ENZYMATIC SYNTHESIS OF ISOMALTO-OLIGOSACCHARIDES PRODUCTIONJOURNAL OF FOOD BIOCHEMISTRY, Issue 3 2009M.C. RABELO ABSTRACT Glucosyltransferases can be applied in the synthesis of prebiotic oligosaccharides. Enzymatic synthesis using acceptors can be used to obtain these carbohydrates. When maltose is the acceptor, oligosaccharides containing one maltose moiety and up to eight glucose units linked by ,-1,6-glycosidic bonds are obtained as the product of dextransucrase acceptor reaction. In this work, the enzymatic synthesis of isomalto-oligosaccharides using dextransucrase from Leuconostoc mesenteroides NRRL B-512F was optimized by response surface methodology. The effect of maltose and sucrose concentrations on the acceptor reaction was evaluated in a batch reactor system. Partially purified enzyme was used to reduce the enzyme purification cost. The results showed that high sucrose concentrations in conjunction with high maltose levels enhanced the isomalto-oligosaccharide synthesis. A productivity of 42.95 mmol/L.h of isomalto-oligosaccharides was obtained at the optimal operating condition (100 mmol/L of sucrose and 200 mmol/L of maltose). PRATICAL APPLICATIONS Oligosaccharides as prebiotic have a large application in food formulations, and their beneficial role in human health have been extensively studied. Although the acceptor mechanism of dextransucrase has already been extensively studied, an industrial process has not been developed yet for enzyme synthesis of isomalto-oligosaccharide. The process studied in this work allows the large-scale preparation of isomalto-oligosaccharide using partially purified enzyme. [source] Ring-opening polymerization of benzylated 1,6-anhydro-,- D -lactose and specific biological activities of sulfated (1,6)-,- D -lactopyranansJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 3 2009Shuqin Han Abstract A new anhydro disaccharide monomer, 1,6-anhydro-2,3-di- o -benzyl-4- o -(2,,3,,4,,6,-tetra- o -benzyl-,- D -galactopyranosyl)-,- D -glucopyranose (benzylated 1,6-anhydro lactose (LSHBE)), was synthesized from D -lactose to investigate the polymerizability and biological activities of the resulting branched polysaccharides. The ring-opening polymerization of LSHBE was carried out with phosphorus pentafluoride as a catalyst under high vacuum to give a stereoregular benzylated (1 , 6)-,- D -lactopyranan. The molecular weights of poly(LSHBE)s increased with an increase in the amount of CH2Cl2 solvent, and polymerization temperatures were affected in both molecular weights and yields of the polymers. The copolymerization of LSHBE with benzylated 1,6-anhydro-,- D -glucopyranose (LGTBE) gave the corresponding copolysacchrides having different proportions of lactose and glucose units in good yields. After debenzylation to recover hydroxyl groups and then sulfation, sulfated homopoly(lactose)s and copoly(lactose and glucose)s were obtained. Sulfated homopoly(lactose)s had moderate anti-HIV (EC50 = 5.9 and 1.3 ,g/mL) and blood anticoagulant activities (AA = 18 and 13 unit/mg), respectively. Sulfated copoly(lactose and glucose) having 15 mol % lactose units gave high anti-HIV and blood anticoagulant activities of 0.3 ,g/mL and 54 unit/mg, respectively. These biological results suggest that the distance between branched units on the main chain plays an important role in the anti-HIV and blood anticoagulant activities. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 913,924, 2009 [source] | |||||||||||||