The Experts below are selected from a list of 264 Experts worldwide ranked by ideXlab platform
Christa Schleper - One of the best experts on this subject based on the ideXlab platform.
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methylotrophic methanogenic thermoplasmata implicated in reduced methane emissions from bovine rumen
Nature Communications, 2013Co-Authors: Morten Poulsen, Clarissa Schwab, Bent Borg Jensen, Ricarda M Engberg, Anja Spang, Nuria Canibe, Ole Hojberg, Gabriel J Milinovich, Lena Fragner, Christa SchleperAbstract:Rumen methanogens are major sources of anthropogenic methane emissions, and these archaea are targets in strategies aimed at reducing methane emissions. Here we show that the poorly characterised Thermoplasmata archaea in bovine rumen are methylotrophic methanogens and that they are reduced upon dietary supplementation with rapeseed oil in lactating cows. In a metatranscriptomic survey, Thermoplasmata 16S rRNA and methyl-coenzyme M reductase (mcr) transcripts decreased concomitantly with mRNAs of enzymes involved in methanogenesis from Methylamines that were among the most abundant archaeal transcripts, indicating that these Thermoplasmata degrade Methylamines. Their methylotrophic methanogenic lifestyle was corroborated by in vitro incubations, showing enhanced growth of these organisms upon methylamine supplementation paralleled by elevated methane production. The Thermoplasmata have a high potential as target in future strategies to mitigate methane emissions from ruminant livestock. Our findings and the findings of others also indicate a wider distribution of methanogens than previously anticipated.
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Methylotrophic methanogenic Thermoplasmata implicated in reduced methane emissions from bovine rumen
Nature Communications, 2013Co-Authors: Morten Poulsen, Clarissa Schwab, Ricarda M Engberg, Anja Spang, Nuria Canibe, Ole Hojberg, Gabriel J Milinovich, Lena Fragner, Bent Borg Jensen, Christa SchleperAbstract:Rumen methanogens are major sources of anthropogenic methane emissions, and these archaea are targets in strategies aimed at reducing methane emissions. Here we show that the poorly characterised Thermoplasmata archaea in bovine rumen are methylotrophic methanogens and that they are reduced upon dietary supplementation with rapeseed oil in lactating cows. In a metatranscriptomic survey, Thermoplasmata 16S rRNA and methyl-coenzyme M reductase ( mcr ) transcripts decreased concomitantly with mRNAs of enzymes involved in methanogenesis from Methylamines that were among the most abundant archaeal transcripts, indicating that these Thermoplasmata degrade Methylamines. Their methylotrophic methanogenic lifestyle was corroborated by in vitro incubations, showing enhanced growth of these organisms upon methylamine supplementation paralleled by elevated methane production. The Thermoplasmata have a high potential as target in future strategies to mitigate methane emissions from ruminant livestock. Our findings and the findings of others also indicate a wider distribution of methanogens than previously anticipated. Rumen methanogenic archaea are major sources of methane emissions and potential targets for methane mitigation strategies. Poulsen et al. now show that dietary rapeseed oil (RSO) supplementation can reduce the abundance of methanogenic Thermoplasmata archaea inhabiting the bovine rumen.
Alfons Baiker - One of the best experts on this subject based on the ideXlab platform.
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synthesis of Methylamines from co2 h2 and nh3 over cu mg al mixed oxides
Journal of Molecular Catalysis A-chemical, 1999Co-Authors: Steffen M Auer, Silvia V Gredig, Rene A Koppel, Alfons BaikerAbstract:Abstract The synthesis of Methylamines from carbon dioxide, hydrogen, and ammonia has been studied over catalysts derived from Cu–Mg–Al lamellar double hydroxides (LDH) with hydrotalcite-like structure. Catalysts containing 33 at.% Cu(II) related to the total metal content, with different ratios of Mg(II) to Al(III), and a binary Cu–Al catalyst containing 67 at.% Cu were prepared by precipitation of metal nitrates with sodium carbonate. The effect of sample composition and of calcination temperature on the catalytic behaviour has been investigated. Catalytic tests were performed in a fixed-bed microreactor in the temperature range 473–573 K and at 0.6 MPa total pressure. Activity for methylamine formation increased for the ternary catalysts with increasing ratio x=M(III)/[M(II)+M(III)]. Maximum activity was observed for a catalyst with x=0.33, for which XRD analysis indicated a pure hydrotalcite-like phase. Increasing the calcination temperature of this sample from 673 K to 773 K improved the activity, whereas a significant loss in activity was observed when calcined at 873 K. This behaviour could be traced to the copper surface area, which increased from 4 to 14 m2 g−1 (773 K) and then decreased to 9 m2 g−1 (873 K), depending on calcination temperature. After catalytic testing the catalysts calcined up to 773 K consisted of dispersed copper in an amorphous oxide matrix, whereas calcination at 873 K caused the additional formation of CuAl2O4. Distribution of the Methylamines was similar for all catalysts with the fraction of monomethylamine being higher than 80%, besides of smaller amounts of di- and trimethylamine. Other carbon containing products observed were carbon monoxide, formed by the reverse water–gas shift reaction (RWGSR), and methanol in the absence of ammonia in the feed. No general correlation between either BET or copper surface area and catalytic activity was observed. However, for the Cu–Mg–Al catalyst with x=0.33 calcined at different temperatures activity for methylamine formation roughly parallelled the copper surface area measured by N2O-titration.
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synthesis of Methylamines from co2 h2 and nh3 catalytic behaviour of various metal alumina catalysts
Applied Catalysis A-general, 1997Co-Authors: Silvia V Gredig, R A Koeppel, Alfons BaikerAbstract:Abstract The synthesis of Methylamines from CO2, H2 and NH3 has been investigated over various metal-alumina catalysts (Cu, Ag, Ni, Pt, Co and Fe) prepared by coprecipitation. Catalytic tests were carried out using a fixed-bed reactor in the temperature range 473–573 K and at 0.6 MPa total pressure. Among all metal catalysts highest methylamine production rates were obtained with the copper-alumina catalysts, affording a distribution of monomethylamine (MMA): dimethylamine (DMA): trimethylamine (TMA) of 72 : 15 : 13 at 513 K. Increasing the ammonia concentration in the feed resulted in improved selectivity to MMA. By-products observed over copper-alumina were carbon monoxide, originating from the reverse water gas shift reaction, and water. Ni, Co, Fe and Pt showed little methylamine production, but significant methane formation, whereas Ag produced only CO, H2O and HCN.
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Palladium catalyzed synthesis of Methylamines from carbon dioxide, hydrogen and ammonia
Catalysis Letters, 1997Co-Authors: Silvia V Gredig, R A Koeppel, Alfons BaikerAbstract:The synthesis of Methylamines from carbon dioxide, hydrogen, and ammonia has been studied over two palladium-alumina catalysts with palladium loadings of 2.8 and 7.6 wt%, respectively. Catalytic tests were performed in a fixed-bed microreactor at 0.6 MPa total pressure in the temperature range 473--573 K. The catalysts showed high activity for methylamine formation at low temperatures and produced monomethylamine with selectivities higher than 80%, besides of smaller amounts of di- and trimethylamine. Other carbon containing products observed were carbon monoxide, formed by the reverse water-gas shift reaction, and methane, which was the prevailing product above 573 K. In situ diffuse reflectance FTIR studies were performed to identify the species present on the catalyst surface under reaction conditions. Ammonia and Methylamines are adsorbed on Bronsted and Lewis acid sites on the catalyst. Evidence is given that surface formate and isocyanate species are present on palladium-alumina under reaction conditions.
Morten Poulsen - One of the best experts on this subject based on the ideXlab platform.
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methylotrophic methanogenic thermoplasmata implicated in reduced methane emissions from bovine rumen
Nature Communications, 2013Co-Authors: Morten Poulsen, Clarissa Schwab, Bent Borg Jensen, Ricarda M Engberg, Anja Spang, Nuria Canibe, Ole Hojberg, Gabriel J Milinovich, Lena Fragner, Christa SchleperAbstract:Rumen methanogens are major sources of anthropogenic methane emissions, and these archaea are targets in strategies aimed at reducing methane emissions. Here we show that the poorly characterised Thermoplasmata archaea in bovine rumen are methylotrophic methanogens and that they are reduced upon dietary supplementation with rapeseed oil in lactating cows. In a metatranscriptomic survey, Thermoplasmata 16S rRNA and methyl-coenzyme M reductase (mcr) transcripts decreased concomitantly with mRNAs of enzymes involved in methanogenesis from Methylamines that were among the most abundant archaeal transcripts, indicating that these Thermoplasmata degrade Methylamines. Their methylotrophic methanogenic lifestyle was corroborated by in vitro incubations, showing enhanced growth of these organisms upon methylamine supplementation paralleled by elevated methane production. The Thermoplasmata have a high potential as target in future strategies to mitigate methane emissions from ruminant livestock. Our findings and the findings of others also indicate a wider distribution of methanogens than previously anticipated.
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Methylotrophic methanogenic Thermoplasmata implicated in reduced methane emissions from bovine rumen
Nature Communications, 2013Co-Authors: Morten Poulsen, Clarissa Schwab, Ricarda M Engberg, Anja Spang, Nuria Canibe, Ole Hojberg, Gabriel J Milinovich, Lena Fragner, Bent Borg Jensen, Christa SchleperAbstract:Rumen methanogens are major sources of anthropogenic methane emissions, and these archaea are targets in strategies aimed at reducing methane emissions. Here we show that the poorly characterised Thermoplasmata archaea in bovine rumen are methylotrophic methanogens and that they are reduced upon dietary supplementation with rapeseed oil in lactating cows. In a metatranscriptomic survey, Thermoplasmata 16S rRNA and methyl-coenzyme M reductase ( mcr ) transcripts decreased concomitantly with mRNAs of enzymes involved in methanogenesis from Methylamines that were among the most abundant archaeal transcripts, indicating that these Thermoplasmata degrade Methylamines. Their methylotrophic methanogenic lifestyle was corroborated by in vitro incubations, showing enhanced growth of these organisms upon methylamine supplementation paralleled by elevated methane production. The Thermoplasmata have a high potential as target in future strategies to mitigate methane emissions from ruminant livestock. Our findings and the findings of others also indicate a wider distribution of methanogens than previously anticipated. Rumen methanogenic archaea are major sources of methane emissions and potential targets for methane mitigation strategies. Poulsen et al. now show that dietary rapeseed oil (RSO) supplementation can reduce the abundance of methanogenic Thermoplasmata archaea inhabiting the bovine rumen.
Deping Wang - One of the best experts on this subject based on the ideXlab platform.
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room temperature copper catalyzed arylation of dimethylamine and methylamine in neat water
Advanced Synthesis & Catalysis, 2015Co-Authors: Deping Wang, Daizhi Kuang, Fuxing Zhang, Chunlin Yang, Xiaoming ZhuAbstract:The first room-temperature copper-catalyzed arylations of dimethylamine and methylamine in neat water have been developed. Using a combination of CuI and 6,7-dihydroquinolin-8(5 H)-one oxime as catalyst, dimethylamine is arylated with various aryl halides to give the corresponding products in good to excellent yields. Further, this catalysis enables the selective arylation of methylamine to afford the high yields of monoarylated Methylamines as the sole products.
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Room‐Temperature Copper‐Catalyzed Arylation of Dimethylamine and Methylamine in Neat Water
Advanced Synthesis & Catalysis, 2015Co-Authors: Deping Wang, Kuang Daizhi, Zhang Fuxing, Yang Chunlin, Zhu XiaomingAbstract:The first room-temperature copper-catalyzed arylations of dimethylamine and methylamine in neat water have been developed. Using a combination of CuI and 6,7-dihydroquinolin-8(5 H)-one oxime as catalyst, dimethylamine is arylated with various aryl halides to give the corresponding products in good to excellent yields. Further, this catalysis enables the selective arylation of methylamine to afford the high yields of monoarylated Methylamines as the sole products.
John S. Mcmurray - One of the best experts on this subject based on the ideXlab platform.
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Hydrodehalogenation of Alkyl Iodides with Base-Mediated Hydrogenation and Catalytic Transfer Hydrogenation: Application to the Asymmetric Synthesis of N‑Protected α‑Methylamines
2016Co-Authors: Pijus K. M, Erson Birtwistle, John S. McmurrayAbstract:ABSTRACT: We report a very mild synthesis of N-protected α-Methylamines from the corresponding amino acids. Carboxyl groups of amino acids are reduced to iodomethyl groups via hydroxymethyl intermediates. Reductive deiodination to methyl groups is achieved by hydrogenation or catalytic transfer hydrogenation under alkaline conditions. Basic hydrodehalogenation is selective for the iodomethyl group over hydrogenolysis-labile protecting groups, such as benzyloxycarbonyl, benzyl ester, benzyl ether, and 9-fluorenyloxymethyl, thus allowing the conversion of virtually any protected amino acid into the corresponding N-protected α-methylamine. In the field of peptidomimetic drug development, the goal isto incorporate nonproteinogenic amino acid surrogates into candidate compounds to introduce new ligand−receptor interactions, to reduce proteolytic susceptibility, and to increase bioavailability. α-Methylamines represent a class of amino acid replacements in which the carboxyl group of the amino acid is converted to a methyl group and which, therefore, can serve as C-terminal amino acid mimics. Indeed, our laboratory reporte
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Hydrodehalogenation of Alkyl Iodides with Base-Mediated Hydrogenation and Catalytic Transfer Hydrogenation: Application to the Asymmetric Synthesis of N‑Protected α‑Methylamines
2015Co-Authors: Pijus K. Mandal, Sanderson J. Birtwistle, John S. McmurrayAbstract:We report a very mild synthesis of N-protected α-Methylamines from the corresponding amino acids. Carboxyl groups of amino acids are reduced to iodomethyl groups via hydroxymethyl intermediates. Reductive deiodination to methyl groups is achieved by hydrogenation or catalytic transfer hydrogenation under alkaline conditions. Basic hydrodehalogenation is selective for the iodomethyl group over hydrogenolysis-labile protecting groups, such as benzyloxycarbonyl, benzyl ester, benzyl ether, and 9-fluorenyloxymethyl, thus allowing the conversion of virtually any protected amino acid into the corresponding N-protected α-methylamine
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hydrodehalogenation of alkyl iodides with base mediated hydrogenation and catalytic transfer hydrogenation application to the asymmetric synthesis of n protected α Methylamines
Journal of Organic Chemistry, 2014Co-Authors: Pijus K Mandal, Sanderson J. Birtwistle, John S. McmurrayAbstract:We report a very mild synthesis of N-protected α-Methylamines from the corresponding amino acids. Carboxyl groups of amino acids are reduced to iodomethyl groups via hydroxymethyl intermediates. Reductive deiodination to methyl groups is achieved by hydrogenation or catalytic transfer hydrogenation under alkaline conditions. Basic hydrodehalogenation is selective for the iodomethyl group over hydrogenolysis-labile protecting groups, such as benzyloxycarbonyl, benzyl ester, benzyl ether, and 9-fluorenyloxymethyl, thus allowing the conversion of virtually any protected amino acid into the corresponding N-protected α-methylamine.