The Experts below are selected from a list of 303 Experts worldwide ranked by ideXlab platform
V. A. Demakov - One of the best experts on this subject based on the ideXlab platform.
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the impact of synthetic Nitriles on the morphology and viability of some bacterial species
Biology Bulletin, 2016Co-Authors: A V Maksimova, M. V. Kuznetsova, V. A. DemakovAbstract:The toxic effects of synthetic Nitriles and Nitrile herbicides on some bacterial species were estimated. Biotests based on bioluminescence revealed that aromatic Nitriles including herbicides had the most significant toxic effect on bacteria, which differed from their effect on eukaryotic cells. It was shown that soil strains of Nitrile-utilizing bacteria were resistant to high concentrations of the studied compounds. The minimal bactericidal concentrations for most of Nitriles were 0.5 M or above. It was demonstrated that exposure to 0.1 and 1 mM bromoxynil solution resulted in a decrease in the linear parameters of the cells of all strains and sufficient changes in the cell surface of Gram-negative bacteria. It was proposed that the toxic effect of aromatic herbicides was caused not only by inactivation of an enzyme of the electron-transport chain but also by damage to the surface structures.
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Effects of Nitriles and Amides on the Growth and Nitrile Hydratase Activity of the Rhodococcus sp. Strain gt1
Applied Biochemistry and Microbiology, 2003Co-Authors: A. Yu. Maksimov, Yu. G. Maksimova, G. V. Ovechkina, M. V. Kuznetsova, S. V. Kozlov, V. A. DemakovAbstract:Effects of some Nitriles and amides, as well as glucose and ammonium, on the growth and the Nitrile hydratase (EC 4.2.1.84) activity of the Rhodococcus sp. strain gt1 isolated from soil were studied. The activity of Nitrile hydratase mainly depended on the carbon and nitrogen supply to cells. The activity of Nitrile hydratase was high in the presence of glucose and ammonium at medium concentrations and decreased at concentrations of glucose of more than 0.3%. Saturated unsubstituted aliphatic Nitriles and amides were found to be a good source of nitrogen and carbon. However, the presence of Nitriles and amides in the medium was not absolutely necessary for the expression of the activity of Nitrile hydratase of the Rhodococcus sp. strain gt1.
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Effects of Nitriles and amides on the growth and the Nitrile hydratase activity of the Rhodococcus sp. strain gt1
Prikladnaia biokhimiia i mikrobiologiia, 2003Co-Authors: A Iu Maksimov, G. V. Ovechkina, M. V. Kuznetsova, Iu G Maksimova, S. V. Kozlov, V. A. DemakovAbstract:Effects of some Nitriles and amides, as well as glucose and ammonium, on the growth and the Nitrile hydratase (EC 4.2.1.84) activity of the Rhodococcus sp. strain gt1 isolated from soil were studied. The activity of Nitrile hydratase mainly depended on carbon and nitrogen supply to cells. The activity of Nitrile hydratase was high in the presence of glucose and ammonium at medium concentrations and decreased at concentrations of glucose more than 0.3%. Saturated unsubstituted aliphatic Nitriles and amides were found to be a good source of nitrogen and carbon. However, the presence of Nitriles and amides in the medium was not absolutely necessary for the expression of the activity of Nitrile hydratase isolated from the Rhodococcus sp. strain gt1.
Mei-xiang Wang - One of the best experts on this subject based on the ideXlab platform.
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Enantioselective Biotransformations of Nitriles in Organic Synthesis
Accounts of Chemical Research, 2015Co-Authors: Mei-xiang WangAbstract:ConspectusThe hydration and hydrolysis of Nitriles are valuable synthetic methods used to prepare carboxamides and carboxylic acids. However, chemical hydration and hydrolysis of Nitriles involve harsh reaction conditions, have low selectivity, and generate large amounts of waste. Therefore, researchers have confined the scope of these reactions to simple Nitrile substrates.However, biological transformations of Nitriles are highly efficient, chemoselective, and environmentally benign, which has led synthetic organic chemists and biotechologists to study these reactions in detail over the last two decades. In nature, biological systems degrade Nitriles via two distinct pathways: nitrilases catalyze the direct hydrolysis of Nitriles to afford carboxylic acids with release of ammonia, and Nitrile hydratases catalyze the conversion of Nitriles into carboxamides, which then furnish carboxylic acids via hydrolysis in the presence of amidases. Researchers have subsequently developed biocatalytic methods into us...
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remarkable electronic and steric effects in the Nitrile biotransformations for the preparation of enantiopure functionalized carboxylic acids and amides implication for an unsaturated carbon carbon bond binding domain of the amidase
Journal of Organic Chemistry, 2007Co-Authors: Ming Gao, Zhi-tang Huang, Dexian Wang, Qiyu Zheng, Mei-xiang WangAbstract:Biotransformations of various functionalized racemic Nitriles catalyzed by Rhodococcus erythropolis AJ270, a Nitrile hydratase/amidase-containing microbial whole-cell catalyst, were studied. While ...
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Enantioselective Biotransformations of Nitriles in Organic Synthesis
Topics in Catalysis, 2005Co-Authors: Mei-xiang WangAbstract:Recent advances in enantioselective biotransformations of Nitriles utilizing Nitrile-hydrolyzing microorganisms and enzymes are summarized in this article. Various examples of biocatalytic synthesis of highly enantiopure carboxylic acids including amino acids, hydroxyl acids, cyclopropanecarboxylic acids and amide derivatives and oxiranecarboxamides are presented. The enantioselectivity of the Nitrile hydratases, nitrilases and amideses is discussed.
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Enantioselective biotransformations of racemic α-substituted phenylacetoNitriles and phenylacetamides using Rhodococcus sp. AJ270
Tetrahedron-asymmetry, 2000Co-Authors: Mei-xiang Wang, Gai-jiao Ji, Zhi-tang Huang, Otto Meth-cohn, Gang Lu, John ColbyAbstract:Abstract Rhodococcus sp. AJ270 is an efficient whole-cell system able to catalyze the stereoselective conversions of racemic α-substituted phenylacetoNitriles and amides under very mild conditions into enantiopure carboxylic acids and derivatives. The Nitrile hydratase involved generally has a broad substrate spectrum against phenylacetoNitriles irrespective of the electronic nature of the α-substituent while the amidase is very sensitive to both the electronic and steric factors of the substituent of amides. The overall enantioselectivity of Nitrile hydrolysis is mainly determined by the combination of selectivities of Nitrile hydratase and of amidase, with the latter being a major contributor. The amidase has high S- enantiocontrol against amides while the Nitrile hydratase exhibits low R -selectivity against Nitriles. The scope and limitations of this enantioselective biotransformation process are discussed.
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A powerful new Nitrile hydratase for organic synthesis — aromatic and heteroaromatic Nitrile hydrolyses — a rationalisation
Tetrahedron Letters, 1995Co-Authors: Otto Meth-cohn, Mei-xiang WangAbstract:Abstract A powerful new Nitrile hydratase organism, Rhodococcus rhodocrous AJ270 has been isolated that efficiently hydrolyses all kinds of Nitriles to amides and/or acids. This paper shows that aromatic and heterocyclic Nitriles are readily hydrolysed to acids but, that those bearing an adjacent-substituent (which may be an ortho substituent or an adjacent heteroatom in the ring) give amides in good yield but only slowly proceed to acids.
Bernard A. Prior - One of the best experts on this subject based on the ideXlab platform.
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The Utilization of Aromatic, Cyclic and Heterocyclic Nitriles by Yeasts
Systematic and Applied Microbiology, 1995Co-Authors: Etienne André Brewis, Johannes P. Van Der Walt, Bernard A. PriorAbstract:Summary The ability of endomycetalial yeast strains representing Candida fabianii, Candida famata, Candida guillierntorulii and Williopsis saturnus to utilize a series of aromatic, cyclic and heteroeyclic Nitriles as nitrogen source was examined. Varying degrees of utilization of these compounds were noted. Sterically hindered Nitrile groups were apparently not utilized. C. fabianii demonstrated the highest rate of 3cyanopyridine conversion by the four yeasts and within 24 h, 100% molar conversion was achieved. The cultivation of C. fabianii with aromatic and heteroeyclic Nitriles and ammonium sulphate as nitrogen source resulted in a low apparently constitutive nitrite- and amide-hydrolyzing activity. With aliphatic Nitriles, a considerably higher specific activity was induced against olefinic aliphatic, heteroeyclic and aromatic Nitriles.
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A Note on the Utilization of Aliphatic Nitriles by Yeasts
Systematic and Applied Microbiology, 1993Co-Authors: Johannes P. Van Der Walt, Etienne André Brewis, Bernard A. PriorAbstract:Summary Nine yeast strains of ascomycetous affinity were examined for their ability to utilize a series of aliphatic mono- and diNitriles as well as their corresponding amides as sole source of nitrogen. The results indicate that while some species failed to utilize these Nitriles, this property nonetheless, does not appear to be uncommon among these microfungi. The consistently coincidental utilization of Nitriles and their corresponding amides indicates that the hydrolysis involves a two-step reaction mediated by Nitrile-hydratase and amidase. The data suggests that some of the Nitrile hydratases might be substrate and strain specific.
John Colby - One of the best experts on this subject based on the ideXlab platform.
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Enantioselective biotransformations of racemic α-substituted phenylacetoNitriles and phenylacetamides using Rhodococcus sp. AJ270
Tetrahedron-asymmetry, 2000Co-Authors: Mei-xiang Wang, Gai-jiao Ji, Zhi-tang Huang, Otto Meth-cohn, Gang Lu, John ColbyAbstract:Abstract Rhodococcus sp. AJ270 is an efficient whole-cell system able to catalyze the stereoselective conversions of racemic α-substituted phenylacetoNitriles and amides under very mild conditions into enantiopure carboxylic acids and derivatives. The Nitrile hydratase involved generally has a broad substrate spectrum against phenylacetoNitriles irrespective of the electronic nature of the α-substituent while the amidase is very sensitive to both the electronic and steric factors of the substituent of amides. The overall enantioselectivity of Nitrile hydrolysis is mainly determined by the combination of selectivities of Nitrile hydratase and of amidase, with the latter being a major contributor. The amidase has high S- enantiocontrol against amides while the Nitrile hydratase exhibits low R -selectivity against Nitriles. The scope and limitations of this enantioselective biotransformation process are discussed.
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Regio- and stereo-specific Nitrile hydrolysis by the Nitrile hydratase from Rhodococcus AJ270
Fems Microbiology Letters, 1995Co-Authors: Alan J. Blakey, Edwin Williams, John Colby, Catherine O’reillyAbstract:An acetoNitrile-utilising bacterium AJ270 has been isolated from soil, identified as a Rhodococcus sp. and shown to be distinct from all the recognised species of the genus. It grows well on 32 of 36 aliphatic, aromatic and hetero-aromatic Nitriles tested and is capable of rapid growth on high concentrations (0.25–0.38 M) of acetoNitrile, benzoNitrile and 3-cyanopyridine. The Nitrile hydratase of Rhodococcus AJ270 is stable on storage for 18 months at − 20° C, has activity against a very broad range of Nitriles and diNitriles and is able to catalyse regio-specific and stereo-specific Nitrile biotransformations. The suitability of AJ270 as a robust and versatile biocatalyst is discussed.
Johannes P. Van Der Walt - One of the best experts on this subject based on the ideXlab platform.
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The Utilization of Aromatic, Cyclic and Heterocyclic Nitriles by Yeasts
Systematic and Applied Microbiology, 1995Co-Authors: Etienne André Brewis, Johannes P. Van Der Walt, Bernard A. PriorAbstract:Summary The ability of endomycetalial yeast strains representing Candida fabianii, Candida famata, Candida guillierntorulii and Williopsis saturnus to utilize a series of aromatic, cyclic and heteroeyclic Nitriles as nitrogen source was examined. Varying degrees of utilization of these compounds were noted. Sterically hindered Nitrile groups were apparently not utilized. C. fabianii demonstrated the highest rate of 3cyanopyridine conversion by the four yeasts and within 24 h, 100% molar conversion was achieved. The cultivation of C. fabianii with aromatic and heteroeyclic Nitriles and ammonium sulphate as nitrogen source resulted in a low apparently constitutive nitrite- and amide-hydrolyzing activity. With aliphatic Nitriles, a considerably higher specific activity was induced against olefinic aliphatic, heteroeyclic and aromatic Nitriles.
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A Note on the Utilization of Aliphatic Nitriles by Yeasts
Systematic and Applied Microbiology, 1993Co-Authors: Johannes P. Van Der Walt, Etienne André Brewis, Bernard A. PriorAbstract:Summary Nine yeast strains of ascomycetous affinity were examined for their ability to utilize a series of aliphatic mono- and diNitriles as well as their corresponding amides as sole source of nitrogen. The results indicate that while some species failed to utilize these Nitriles, this property nonetheless, does not appear to be uncommon among these microfungi. The consistently coincidental utilization of Nitriles and their corresponding amides indicates that the hydrolysis involves a two-step reaction mediated by Nitrile-hydratase and amidase. The data suggests that some of the Nitrile hydratases might be substrate and strain specific.
