- Quantitative analysis and functional evaluation of zinc ion in the D-hydantoinase from Pseudomonas putida YZ-26
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D-Hydantoinase (HDT) is a metal-dependent enzyme that is widely used in industrial bioconversion to D-amino acids as valuable intermediates in the fields of food, pharmaceutical industry and agriculture. In this report, we prepared apo-HDT (metal-removed HDT) and Zn2+-HDT (Zn 2+-added HDT) in vitro from a recombinant HDT (re-HDT) expressed in E. coli. The Zn2+-HDT and re-HDT contain 2.17 and 0.95 mol Zn 2+ per mol subunit, respectively, and they have comparable enzymatic activities. In contrast, the apo-HDT only retains 0.04 mol Zn2+ per mol subunit with less than 10% activity, compared with the re-HDT. When the apo-HDT was reconstituted with ZnCl2, the enzymatic activity recovery was about 75%. Moreover, the fluorescence intensity, circular dichroism spectra and thermo-stability of the apo-HDT and Zn2+-HDT are quite different from those of the re-HDT. These data suggest that the re-HDT may have two Zn2+-binding sites, one is an intrinsic or tight-binding site (zinc-α) essential for its activity and the other is a vacant or loose-binding site (zinc-β) possibly non-essential for the activity. Springer Science+Business Media.
- Zhang, Xueyao,Yuan, Jingming,Niu, Lixi,Liang, Aihua
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Read Online
- A practically simple, catalyst free and scalable synthesis of: N -substituted ureas in water
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A practically simple, mild and efficient method is developed for the synthesis of N-substituted ureas by nucleophilic addition of amines to potassium isocyanate in water without organic co-solvent. Using this methodology, a variety of N-substituted ureas (mono-, di- and cyclic-) were synthesized in good to excellent yields with high chemical purity by applying simple filtration or routine extraction procedures avoiding silica gel purification. The developed methodology was also found to be suitable for gram scale synthesis of molecules having commercial application in large volumes. The identified reaction conditions were found to promote a unique substrate selectivity from a mixture of two amines.
- Tiwari, Lata,Kumar, Varun,Kumar, Bhuvesh,Mahajan, Dinesh
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p. 21585 - 21595
(2018/06/26)
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- PROCESS FOR STRAIGHTENING KERATIN FIBRES WITH A HEATING MEANS AND DENATURING AGENTS
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The invention relates to a process for straightening keratin fibres, comprising: (i) a step in which a straightening composition containing at least two denaturing agents is applied to the keratin fibres, (ii) a step in which the temperature of the keratin fibres is raised, using a heating means, to a temperature of between 110 and 250° C.
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- Synthesis of pyrimidines and triazines in ice: Implications for the prebiotic chemistry of nucleobases
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Herein, we report the efficient synthesis of RNA bases and func-tionalized s-triazines from 0.1 M urea solutions in water after subjection to freeze-thaw cycles for three weeks. The icy solution was under a reductive, methane-based atmosphere, which was s
- Menor-Salvan, Cesar,Ruiz-Bermejo, Dra. Marta,Guzman, Marcelo I.,Osuna-Esteban, Susana,Veintemillas-Verdaguer, Sabino
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experimental part
p. 4411 - 4418
(2009/12/07)
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- The peptide formation mediated by cyanate revisited. N-carboxyanhydrides as accessible intermediates in the decomposition of N-carbamoylamino acids
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Similar to many ureas, N-carbamoylamino acids were shown to be hydrolyzed in aqueous solution through elimination mechanisms at close to neutral pH, the nucleophilic attack of water being a minor process. Two competing elimination mechanisms can take place involving either cyanate or isocyanate transient intermediates. Peptide formation was observed and attributed to the latter pathway through the intermediacy of amino acid N-carboxyanhydride (NCA). Eventually, cyanate and its precursors (including urea) unexpectedly behave as amino acid activating agents because of their ability in amino acid carbamoylation. Owing to its ability to generate a background prebiotic production of NCAs on the primitive Earth, this reaction is suggested to have contributed to the origin of life process. Copyright
- Danger, Gregoire,Boiteau, Laurent,Cottet, Herve,Pascal, Robert
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p. 7412 - 7413
(2007/10/05)
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- Synthesis of 2-monofunctionalized 2,4,6,8-tetraazabicyclo[3.3.0]octane-3,7- diones
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New (1R*,5S*)-2-R-2,4,6,8-tetraazabicyclo[3.3.0]octane-3,7- diones containing the terminal carboxy or hydroxy group in the substituent R were synthesized by cyclocondensation of 4,5-dihydroxyimidazolidin-2-one with 1-R-ureas. Single-crystal X-ray diffraction analysis showed that 2-carboxyethyl-2,4,6,8-tetraazabicyclo[3.3.0]octane-3,7-dione crystallizes as a racemate.
- Kravchenko,Maksareva,Belyakov,Sigachev,Chegaev,Lyssenko,Lebedev,Makhova
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p. 192 - 197
(2007/10/03)
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- New functional glycoluril derivatives
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Functional glycoluril (2,4,6,8-tetraazabicyclo[3.3.0]octan-3,7-dione) derivatives containing 2-hydroxyethyl, carboxyl and amino groups were synthesised.
- Chegaev,Kravchenko,Lebedev,Strelenko
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- A pH-dependent cyanate reactivity model: Application to preparative N-carbamoylation of amino acids
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Recent developments in peptide synthesis have underlined the importance of optimising, on a preparative scale, the N-carbamoylation of amino acids by aqueous cyanate. To this purpose, a theoretical model of aqueous cyanate reactivity was designed. The parameters of the model were evaluated, for various pH and temperatures, from a critical survey of the literature, together with additional experimental data. Computer-simulated kinetics based on this model showed the reaction efficiency to be significantly dependent on pH, and suggested optimum conditions to be moderate temperatures and pH 8.5-9. Discussion of the practical convenience of these theoretical results led us to prefer 40-50 °C and a pH range of 7-8 as reaction conditions, thus maintaining reaction times within a few hours. Various N-carbamoyl amino acids (ureido derivatives of glycine, L-valine, L-alanine, L-leucine, DL-methionine, Nε-trifluoroacetyl-L-lysine, β-alanine) were thus successfully synthesised on the gram to kilogram scales.
- Taillades, Jacques,Boiteau, Laurent,Beuzelin, Isabelle,Lagrille, Olivier,Biron, Jean-Philippe,Vayaboury, Willy,Vandenabeele-Trambouze, Odile,Giani, Olivia,Commeyras, Auguste
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p. 1247 - 1254
(2007/10/03)
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- Mechanism of Asymmetric Production of D-Amino Acids from the Corresponding Hydantoins by Pseudomonas sp.
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The mechanism of asymmetric production of D-amino acids from the corresponding hydantoins by Pseudomonas sp.AJ-11220 was examined by investigating the properties of the enzymes involved in the hydrolysis of DL-5-substituted hydantoins.The enzymatic production of D-amino acids from the corresponding hydantoins by Pseudomonas sp.AJ-11220 involved the following two successive reactions; the D-isomer specific hydrolysis, i.e., the ring opening of D-5-substituted hydantoins to D-form N-carbamyl amino acids by an enzyme, D-hydantoin hydrolase (D-HYD hydrolase), followed by the D-isomer specific hydrolysis, i.e., the cleavage of N-carbamyl-D-amino acids to D-amino acids by an enzyme, N-carbamyl-D-amino acid hydrolase (D-NCA hydrolase).L-5-Substituted hydantoins not hydrolyzed by D-HYD hydrolase were converted to D-form 5-substituted hydantoins through spontaneous racemization under the enzymatic reaction conditions.It was proposed that almost all of the DL-5-substituted hydantoins were stoichiometrically and directly converted to the corresponding D-amino acids through the successive reactions of D-HYD hydrolase and D-NCA hydrolase in parallel with the spontaneous racemization of L-5-substituted hydantoins to those of DL-form.
- Yokozeki, Kenzo,Kubota, Koji
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p. 721 - 728
(2007/10/02)
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- Peptides 119. - Peptide Synthesis with N-Carboxy-α-amino Acid Anhydrides
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On reaction of N-carboxy-α-amino acid anhydrides (NCA) with equimolar amounts of aminoacids or excess NCA in potassium borate buffer of pH 10.2 (0 deg C) considerable amounts of homooligomers and homopolymers are formed.If an excess of amino acid is used formation of the above mentioned by-products can be suppressed.The extent of homooligomerization and homopolymerization and hydrolysis occurring during the reaction of NCA under the conditions of peptide synthesis is described.
- Kircher, K.,Berndt, H.,Zahn, H.
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p. 275 - 284
(2007/10/02)
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