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Brad Bendiak – One of the best experts on this subject based on the ideXlab platform.

  • Direct evidence for the ring opening of monosaccharide anions in the gas phase: photodissociation of Aldohexoses and Aldohexoses derived from disaccharides using variable-wavelength infrared irradiation in the carbonyl stretch region
    Carbohydrate Research, 2011
    Co-Authors: Darin J. Brown, Sarah E. Stefan, Giel Berden, Jeffrey D. Steill, Jos Oomens, John R. Eyler, Brad Bendiak

    Abstract:

    All eight D-Aldohexoses and Aldohexoses derived from the non-reducing end of disaccharides were investigated by variable-wavelength infrared multiple-photon dissociation (IRMPD) as anions in the negative-ion mode. Spectroscopic evidence supports the existence of a relatively abundant open-chain configuration of the anions in the gas phase, based on the observation of a significant carbonyl absorption band near 1710 cm(-1). The abundance of the open-chain configuration of the aldohexose anions was approximately 1000-fold or greater than that of the neutral sugars in aqueous solution. This provides an explanation as to why it has not been possible to discriminate the anomeric configuration of aldohexose anions in the gas phase when derived from the non-reducing sugar of a disaccharide. Evidence from photodissociation spectra also indicates that the different Aldohexoses yield product ions with maximal abundances at different wavelengths, and that the carbonyl stretch region is useful for differentiation of sugar stereochemistries. Quantum-chemical calculations indicate relatively low energy barriers to intramolecular proton transfer between hydroxyl groups and adjacent alkoxy sites located on open-chain sugar anions, suggesting that an ensemble of alkoxy charge locations contributes to their observed photodissociation spectra. Ring opening of monosaccharide anions and interconversion among configurations is an inherent property of the ions themselves and occurs in vacuo independent of solvent participation. (C) 2011 Elsevier Ltd. All rights reserved.

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  • end group determination of oligosaccharides a gas chromatography mass spectrometry mass spectrometry method for distinguishing between all d Aldohexoses and d ketohexoses
    Carbohydrate Research, 2000
    Co-Authors: Brad Bendiak, Tammy T. Fang

    Abstract:

    Abstract A method for end-group determination of oligosaccharides is described, which involves conversion of the reducing monosaccharide into a 1-deoxy-1-hydrazinohexitol heptaacetate (Aldohexoses) or an epimeric pair of 2-deoxy-2-hydrazinohexitol heptaacetates (2-ketohexoses). Products are linear and unique to each aldohexose or ketohexose. Methods are reported for separation of all stereoisomers of the derivatives on single columns by gas chromatography. Gas chromatography–mass spectrometry/mass spectrometry with electron-impact ionization enabled the 1-deoxy-1-hydrazinohexitol heptaacetates and 2-deoxy-2-hydrazinohexitol heptaacetates to be independently identified in each others presence. Chemical-ionization mass spectrometry/mass spectrometry permitted derivatives to be identified in subpicomolar quantities. The non-acetylated compounds could also be identified as their hydrochlorides by 1H NMR spectroscopy.

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  • End-group determination of oligosaccharides: a gas chromatography-mass spectrometry/mass spectrometry method for distinguishing between all D-Aldohexoses and D-ketohexoses.
    Carbohydrate Research, 2000
    Co-Authors: Brad Bendiak, Tammy T. Fang

    Abstract:

    Abstract A method for end-group determination of oligosaccharides is described, which involves conversion of the reducing monosaccharide into a 1-deoxy-1-hydrazinohexitol heptaacetate (Aldohexoses) or an epimeric pair of 2-deoxy-2-hydrazinohexitol heptaacetates (2-ketohexoses). Products are linear and unique to each aldohexose or ketohexose. Methods are reported for separation of all stereoisomers of the derivatives on single columns by gas chromatography. Gas chromatography–mass spectrometry/mass spectrometry with electron-impact ionization enabled the 1-deoxy-1-hydrazinohexitol heptaacetates and 2-deoxy-2-hydrazinohexitol heptaacetates to be independently identified in each others presence. Chemical-ionization mass spectrometry/mass spectrometry permitted derivatives to be identified in subpicomolar quantities. The non-acetylated compounds could also be identified as their hydrochlorides by 1H NMR spectroscopy.

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Bert M Weckhuysen – One of the best experts on this subject based on the ideXlab platform.

  • Base‐free Pd/TOMPP‐Catalyzed Telomerization of 1,3‐Butadiene with Carbohydrates and Sugar Alcohols
    Chemsuschem, 2009
    Co-Authors: Peter J. C. Hausoul, Pieter C A Bruijnincx, Robertus J. M. Klein Gebbink, Bert M Weckhuysen

    Abstract:

    Sugar and alcohol – a superior combo: The telomerization activity of the Pd/TOMPP catalyst is screened using thirteen different biomass-derived carbohydrates and sugar alcohols. High substrate conversions are achieved by using low Pd loading and without the use of an added base. In terms of butadiene conversion, a clear structure-activity relationship is found, which is in line with the series: sugar alcohols>sucrose>Aldohexoses>aldopentoses>ketohexoses

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  • base free pd tompp catalyzed telomerization of 1 3 butadiene with carbohydrates and sugar alcohols
    Chemsuschem, 2009
    Co-Authors: Peter J. C. Hausoul, Pieter C A Bruijnincx, Robertus J. M. Klein Gebbink, Bert M Weckhuysen

    Abstract:

    Sugar and alcohol – a superior combo: The telomerization activity of the Pd/TOMPP catalyst is screened using thirteen different biomass-derived carbohydrates and sugar alcohols. High substrate conversions are achieved by using low Pd loading and without the use of an added base. In terms of butadiene conversion, a clear structure-activity relationship is found, which is in line with the series: sugar alcohols>sucrose>Aldohexoses>aldopentoses>ketohexoses

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Tomohiro Tamura – One of the best experts on this subject based on the ideXlab platform.

  • C-terminal tail derived from the neighboring subunit is critical for the activity of Thermoplasma acidophilum D-aldohexose dehydrogenase.
    Proteins: Structure Function and Bioinformatics, 2009
    Co-Authors: Taiki Nishioka, Yoshiaki Yasutake, Yoshiaki Nishiya, Noriko Tamura, Tomohiro Tamura

    Abstract:

    The D-aldohexose dehydrogenase from the thermoacidophilic archaeon Thermoplasma acidophilum (AldT) is a homotetrameric enzyme that catalyzes the oxidation of several D-Aldohexoses, especially D-mannose. AldT comprises a unique C-terminal tail motif (residues 247–255) that shuts the active-site pocket of the neighboring subunit. The functional role of the C-terminal tail of AldT has been investigated using mutational and crystallographic analyses. A total of four C-terminal deletion mutants (Δ254, Δ253, Δ252, and Δ249) and two site-specific mutants (Y86G and P254G) were expressed by Escherichia coli and purified. Enzymatic characterization of these mutants revealed that the C-terminal tail is a requisite and that the interaction between Tyr86 and Pro254 is critical for enzyme activity. The crystal structure of the Δ249 mutant was also determined. The structure showed that the active-site loops undergo a significant conformational change, which leads to the structural deformation of the substrate-binding pocket. Proteins 2009. © 2008 Wiley-Liss, Inc.

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  • Crystallization and preliminary crystallographic analysis of NAD+-preferring aldohexose dehydrogenase from the thermoacidophilic archaeon Thermoplasma acidophilum.
    Acta crystallographica. Section F Structural biology and crystallization communications, 2006
    Co-Authors: Yoshiaki Yasutake, Yoshiaki Nishiya, Noriko Tamura, Tomohiro Tamura

    Abstract:

    The aldohexose dehydrogenase from the thermoacidophilic archaeon Thermoplasma acidophilum (AldT) is a 28 kDa molecular-weight enzyme that catalyzes the oxidation of various Aldohexoses, with a preference for NAD+ rather than NADP+ as a cofactor. The recombinant AldT was crystallized using the hanging-drop vapour-diffusion technique at 293 K under several acidic conditions with polyethylene glycol (PEG) and ammonium sulfate as precipitants. Optimization of the initial crystallizations conditions yielded single crystals in solution containing 0.1 M sodium acetate pH 4.6, 18%(w/v) PEG 4000, 0.2 M ammonium sulfate and 15%(v/v) glycerol. An X-ray diffraction data set was collected to a resolution of 2.8 A.

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  • Analysis of bacterial glucose dehydrogenase homologs from thermoacidophilic archaeon Thermoplasma acidophilum: finding and characterization of aldohexose dehydrogenase.
    Bioscience Biotechnology and Biochemistry, 2004
    Co-Authors: Yoshiaki Nishiya, Noriko Tamura, Tomohiro Tamura

    Abstract:

    The NADP+-preferring glucose dehydrogenase from thermoacidophilic archaeon Thermoplasma acidophilum has been characterized, and its crystal structure has been determined (Structure, 2:385-393, 1994). Its sequence and structure are not homologous to bacterial NAD(P)+-dependent glucose dehydrogenases, and its molecular weight is also quite defferent. On the other hand, three functionally unknown genes with homologies to bacterial NAD(P)+-dependent glucose dehydrogenases have been sequenced as part of the T. acidophilum genome project (gene names: Ta0191, Ta0747, and Ta0754 respectively). We expressed two genes of three, Ta0191 and Ta0754, in Escherichia coli, and purified the gene products to homogeneity. Dehydrogenase activities were thereby detected from the purified proteins. The Ta0754 gene product exhibited aldohexose dehydrogenase activity, and the Ta0191 gene product exhibited weak 2-deoxyglucose dehydrogenase activity. No aldohexose dehydrogenase gene has been isolated, while the enzyme was reported…

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