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Robert H. White - One of the best experts on this subject based on the ideXlab platform.
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Biochemical origins of lactaldehyde and Hydroxyacetone in Methanocaldococcus jannaschii.
Biochemistry, 2008Co-Authors: Robert H. WhiteAbstract:The biochemical routes for the metabolism of methylglyoxal and the formation of lactaldehyde and Hydroxyacetone in Methanocaldococcus jannaschii have been established. The addition of methylglyoxal and NADH, NADPH, F420H2, or DTT to a M. jannaschii cell extract stimulated the production of both lactaldehyde and Hydroxyacetone. Using appropriately labeled NADH, NADPH, and F420H2, hydride transfer was only observed from F420H2 to lactaldehyde. It was shown that cell extracts of this Archaea readily catalyzed the F420H2-dependent reduction of methylglyoxal to lactaldehyde, a precursor of the lactate found in coenzyme F420. This conversion was established by measuring the incorporation of deuterium from (5RS)[5-2H1]F420H2 into the C-2 position of the formed lactaldehyde. In vivo generated (5R)[5-2H1]F420H2 was also found to incorporate deuterium into lactaldehyde. The experimental data indicated that the pro-R hydrogen of F420H2 was transferred during the reduction. The stereochemistry of this transfer was op...
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l aspartate semialdehyde and a 6 deoxy 5 ketohexose 1 phosphate are the precursors to the aromatic amino acids in methanocaldococcus jannaschii
Biochemistry, 2004Co-Authors: Robert H. WhiteAbstract:No orthologs are present in the genomes of the archaea encoding genes for the first two steps in the biosynthesis of the aromatic amino acids leading to 3-dehydroquinate (DHQ). The absence of these genes prompted me to examine the nature of the reactions involved in the archaeal pathway leading to DHQ in Methanocaldococcus jannaschii. Here I report that 6-deoxy-5-ketofructose 1-phosphate and l-aspartate semialdehyde are precursors to DHQ. The sugar, which is derived from glucose 6-P, supplies a “Hydroxyacetone” fragment, which, via a transaldolase reaction, undergoes an aldol condensation with the l-aspartate semialdehyde to form 2-amino-3,7-dideoxy-d-threo-hept-6-ulosonic acid. Despite the fact that both Hydroxyacetone and Hydroxyacetone-P were measured in the cell extracts and confirmed to arise from glucose 6-P, neither compound was found to serve as a precursor to DHQ. This amino sugar then undergoes a NAD dependent oxidative deamination to produce 3,7-dideoxy-d-threo-hept-2,6-diulosonic acid which cy...
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l aspartate semialdehyde and a 6 deoxy 5 ketohexose 1 phosphate are the precursors to the aromatic amino acids in methanocaldococcus jannaschii
Biochemistry, 2004Co-Authors: Robert H. WhiteAbstract:No orthologs are present in the genomes of the archaea encoding genes for the first two steps in the biosynthesis of the aromatic amino acids leading to 3-dehydroquinate (DHQ). The absence of these genes prompted me to examine the nature of the reactions involved in the archaeal pathway leading to DHQ in Methanocaldococcus jannaschii. Here I report that 6-deoxy-5-ketofructose 1-phosphate and l-aspartate semialdehyde are precursors to DHQ. The sugar, which is derived from glucose 6-P, supplies a "Hydroxyacetone" fragment, which, via a transaldolase reaction, undergoes an aldol condensation with the l-aspartate semialdehyde to form 2-amino-3,7-dideoxy-D-threo-hept-6-ulosonic acid. Despite the fact that both Hydroxyacetone and Hydroxyacetone-P were measured in the cell extracts and confirmed to arise from glucose 6-P, neither compound was found to serve as a precursor to DHQ. This amino sugar then undergoes a NAD dependent oxidative deamination to produce 3,7-dideoxy-d-threo-hept-2,6-diulosonic acid which cyclizes to 3-dehydroquinate. The protein product of the M. jannaschii MJ0400 gene catalyzes the transaldolase reaction and the protein product of the MJ1249 gene catalyzes the oxidative deamination and the cyclization reactions. The DHQ is readily converted into dehydroshikimate and shikimate in M. jannaschii cell extracts, consistent with the remaining steps and genes in the pathway being the same as in the established shikimate pathway.
Paul O. Wennberg - One of the best experts on this subject based on the ideXlab platform.
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Quantification of Hydroxyacetone and glycolaldehyde using chemical ionization mass spectrometry
Atmospheric Chemistry and Physics, 2014Co-Authors: J. M. St. Clair, John D. Crounse, Fabien Paulot, K. M. Spencer, M. R. Beaver, Paul O. WennbergAbstract:Abstract. Chemical ionization mass spectrometry (CIMS) enables online, rapid, in situ detection and quantification of Hydroxyacetone and glycolaldehyde. Two different CIMS approaches are demonstrated employing the strengths of single quadrupole mass spectrometry and triple quadrupole (tandem) mass spectrometry. Both methods are generally capable of the measurement of Hydroxyacetone, an analyte with known but minimal isobaric interferences. Tandem mass spectrometry provides direct separation of the isobaric compounds glycolaldehyde and acetic acid using distinct, collision-induced dissociation daughter ions. The single quadrupole CIMS measurement of glycolaldehyde was demonstrated during the ARCTAS-CARB (Arctic Research of the Composition of the Troposphere from Aircraft and Satellites - California Air Resources Board) 2008 campaign, while triple quadrupole CIMS measurements of glycolaldehyde and Hydroxyacetone were demonstrated during the BEARPEX (Biosphere Effects on Aerosols and Photochemistry Experiment) 2009 campaign. Enhancement ratios of glycolaldehyde in ambient biomass-burning plumes are reported for the ARCTAS-CARB campaign. BEARPEX observations are compared to simple photochemical box model predictions of biogenic volatile organic compound oxidation at the site.
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Atmospheric fate of methacrolein. 1. Peroxy radical isomerization following addition of OH and O2.
The journal of physical chemistry. A, 2012Co-Authors: John D. Crounse, Henrik G. Kjaergaard, Hasse C. Knap, Kristian Baruël Ørnsø, Solvejg Jørgensen, Fabien Paulot, Paul O. WennbergAbstract:Peroxy radicals formed by addition of OH and O2 to the olefinic carbon atoms in methacrolein react with NO to form methacrolein hydroxy nitrate and Hydroxyacetone. We observe that the ratio of these two compounds, however, unexpectedly decreases as the lifetime of the peroxy radical increases. We propose that this results from an isomerization involving the 1,4-H-shift of the aldehydic hydrogen atom to the peroxy group. The inferred rate (0.5 ± 0.3 s–1 at T = 296 K) is consistent with estimates obtained from the potential energy surface determined by high level quantum calculations. The product, a hydroxy hydroperoxy carbonyl radical, decomposes rapidly, producing Hydroxyacetone and re-forming OH. Simulations using a global chemical transport model suggest that most of the methacrolein hydroxy peroxy radicals formed in the atmosphere undergo isomerization and decomposition.
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Atmospheric Fate of Methacrolein. 1. Peroxy Radical Isomerization Following Addition of OH and O2
2012Co-Authors: John D. Crounse, Henrik G. Kjaergaard, Hasse C. Knap, Kristian Baruël Ørnsø, Solvejg Jørgensen, Fabien Paulot, Paul O. WennbergAbstract:Peroxy radicals formed by addition of OH and O2 to the olefinic carbon atoms in methacrolein react with NO to form methacrolein hydroxy nitrate and Hydroxyacetone. We observe that the ratio of these two compounds, however, unexpectedly decreases as the lifetime of the peroxy radical increases. We propose that this results from an isomerization involving the 1,4-H-shift of the aldehydic hydrogen atom to the peroxy group. The inferred rate (0.5 ± 0.3 s–1 at T = 296 K) is consistent with estimates obtained from the potential energy surface determined by high level quantum calculations. The product, a hydroxy hydroperoxy carbonyl radical, decomposes rapidly, producing Hydroxyacetone and re-forming OH. Simulations using a global chemical transport model suggest that most of the methacrolein hydroxy peroxy radicals formed in the atmosphere undergo isomerization and decomposition
John D. Crounse - One of the best experts on this subject based on the ideXlab platform.
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Quantification of Hydroxyacetone and glycolaldehyde using chemical ionization mass spectrometry
Atmospheric Chemistry and Physics, 2014Co-Authors: J. M. St. Clair, John D. Crounse, Fabien Paulot, K. M. Spencer, M. R. Beaver, Paul O. WennbergAbstract:Abstract. Chemical ionization mass spectrometry (CIMS) enables online, rapid, in situ detection and quantification of Hydroxyacetone and glycolaldehyde. Two different CIMS approaches are demonstrated employing the strengths of single quadrupole mass spectrometry and triple quadrupole (tandem) mass spectrometry. Both methods are generally capable of the measurement of Hydroxyacetone, an analyte with known but minimal isobaric interferences. Tandem mass spectrometry provides direct separation of the isobaric compounds glycolaldehyde and acetic acid using distinct, collision-induced dissociation daughter ions. The single quadrupole CIMS measurement of glycolaldehyde was demonstrated during the ARCTAS-CARB (Arctic Research of the Composition of the Troposphere from Aircraft and Satellites - California Air Resources Board) 2008 campaign, while triple quadrupole CIMS measurements of glycolaldehyde and Hydroxyacetone were demonstrated during the BEARPEX (Biosphere Effects on Aerosols and Photochemistry Experiment) 2009 campaign. Enhancement ratios of glycolaldehyde in ambient biomass-burning plumes are reported for the ARCTAS-CARB campaign. BEARPEX observations are compared to simple photochemical box model predictions of biogenic volatile organic compound oxidation at the site.
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Atmospheric fate of methacrolein. 1. Peroxy radical isomerization following addition of OH and O2.
The journal of physical chemistry. A, 2012Co-Authors: John D. Crounse, Henrik G. Kjaergaard, Hasse C. Knap, Kristian Baruël Ørnsø, Solvejg Jørgensen, Fabien Paulot, Paul O. WennbergAbstract:Peroxy radicals formed by addition of OH and O2 to the olefinic carbon atoms in methacrolein react with NO to form methacrolein hydroxy nitrate and Hydroxyacetone. We observe that the ratio of these two compounds, however, unexpectedly decreases as the lifetime of the peroxy radical increases. We propose that this results from an isomerization involving the 1,4-H-shift of the aldehydic hydrogen atom to the peroxy group. The inferred rate (0.5 ± 0.3 s–1 at T = 296 K) is consistent with estimates obtained from the potential energy surface determined by high level quantum calculations. The product, a hydroxy hydroperoxy carbonyl radical, decomposes rapidly, producing Hydroxyacetone and re-forming OH. Simulations using a global chemical transport model suggest that most of the methacrolein hydroxy peroxy radicals formed in the atmosphere undergo isomerization and decomposition.
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Atmospheric Fate of Methacrolein. 1. Peroxy Radical Isomerization Following Addition of OH and O2
2012Co-Authors: John D. Crounse, Henrik G. Kjaergaard, Hasse C. Knap, Kristian Baruël Ørnsø, Solvejg Jørgensen, Fabien Paulot, Paul O. WennbergAbstract:Peroxy radicals formed by addition of OH and O2 to the olefinic carbon atoms in methacrolein react with NO to form methacrolein hydroxy nitrate and Hydroxyacetone. We observe that the ratio of these two compounds, however, unexpectedly decreases as the lifetime of the peroxy radical increases. We propose that this results from an isomerization involving the 1,4-H-shift of the aldehydic hydrogen atom to the peroxy group. The inferred rate (0.5 ± 0.3 s–1 at T = 296 K) is consistent with estimates obtained from the potential energy surface determined by high level quantum calculations. The product, a hydroxy hydroperoxy carbonyl radical, decomposes rapidly, producing Hydroxyacetone and re-forming OH. Simulations using a global chemical transport model suggest that most of the methacrolein hydroxy peroxy radicals formed in the atmosphere undergo isomerization and decomposition
Fabien Paulot - One of the best experts on this subject based on the ideXlab platform.
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Quantification of Hydroxyacetone and glycolaldehyde using chemical ionization mass spectrometry
Atmospheric Chemistry and Physics, 2014Co-Authors: J. M. St. Clair, John D. Crounse, Fabien Paulot, K. M. Spencer, M. R. Beaver, Paul O. WennbergAbstract:Abstract. Chemical ionization mass spectrometry (CIMS) enables online, rapid, in situ detection and quantification of Hydroxyacetone and glycolaldehyde. Two different CIMS approaches are demonstrated employing the strengths of single quadrupole mass spectrometry and triple quadrupole (tandem) mass spectrometry. Both methods are generally capable of the measurement of Hydroxyacetone, an analyte with known but minimal isobaric interferences. Tandem mass spectrometry provides direct separation of the isobaric compounds glycolaldehyde and acetic acid using distinct, collision-induced dissociation daughter ions. The single quadrupole CIMS measurement of glycolaldehyde was demonstrated during the ARCTAS-CARB (Arctic Research of the Composition of the Troposphere from Aircraft and Satellites - California Air Resources Board) 2008 campaign, while triple quadrupole CIMS measurements of glycolaldehyde and Hydroxyacetone were demonstrated during the BEARPEX (Biosphere Effects on Aerosols and Photochemistry Experiment) 2009 campaign. Enhancement ratios of glycolaldehyde in ambient biomass-burning plumes are reported for the ARCTAS-CARB campaign. BEARPEX observations are compared to simple photochemical box model predictions of biogenic volatile organic compound oxidation at the site.
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Atmospheric fate of methacrolein. 1. Peroxy radical isomerization following addition of OH and O2.
The journal of physical chemistry. A, 2012Co-Authors: John D. Crounse, Henrik G. Kjaergaard, Hasse C. Knap, Kristian Baruël Ørnsø, Solvejg Jørgensen, Fabien Paulot, Paul O. WennbergAbstract:Peroxy radicals formed by addition of OH and O2 to the olefinic carbon atoms in methacrolein react with NO to form methacrolein hydroxy nitrate and Hydroxyacetone. We observe that the ratio of these two compounds, however, unexpectedly decreases as the lifetime of the peroxy radical increases. We propose that this results from an isomerization involving the 1,4-H-shift of the aldehydic hydrogen atom to the peroxy group. The inferred rate (0.5 ± 0.3 s–1 at T = 296 K) is consistent with estimates obtained from the potential energy surface determined by high level quantum calculations. The product, a hydroxy hydroperoxy carbonyl radical, decomposes rapidly, producing Hydroxyacetone and re-forming OH. Simulations using a global chemical transport model suggest that most of the methacrolein hydroxy peroxy radicals formed in the atmosphere undergo isomerization and decomposition.
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Atmospheric Fate of Methacrolein. 1. Peroxy Radical Isomerization Following Addition of OH and O2
2012Co-Authors: John D. Crounse, Henrik G. Kjaergaard, Hasse C. Knap, Kristian Baruël Ørnsø, Solvejg Jørgensen, Fabien Paulot, Paul O. WennbergAbstract:Peroxy radicals formed by addition of OH and O2 to the olefinic carbon atoms in methacrolein react with NO to form methacrolein hydroxy nitrate and Hydroxyacetone. We observe that the ratio of these two compounds, however, unexpectedly decreases as the lifetime of the peroxy radical increases. We propose that this results from an isomerization involving the 1,4-H-shift of the aldehydic hydrogen atom to the peroxy group. The inferred rate (0.5 ± 0.3 s–1 at T = 296 K) is consistent with estimates obtained from the potential energy surface determined by high level quantum calculations. The product, a hydroxy hydroperoxy carbonyl radical, decomposes rapidly, producing Hydroxyacetone and re-forming OH. Simulations using a global chemical transport model suggest that most of the methacrolein hydroxy peroxy radicals formed in the atmosphere undergo isomerization and decomposition
Miquel A Pericas - One of the best experts on this subject based on the ideXlab platform.
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continuous flow enantioselective three component anti mannich reactions catalyzed by a polymer supported threonine derivative
ACS Catalysis, 2014Co-Authors: Carles Ayats, Andrea H Henseler, Estefania Dibello, Miquel A PericasAbstract:A series of primary amino acid-derived polystyrene-supported organocatalysts was tested in anti-selective Mannich reactions. The polystyrene-immobilized threonine derivative showed the best performance in three-component (Hydroxyacetone, anilines, and aldehydes) Mannich reactions to provide anti-β-amino-α-hydroxycarbonyl compounds (11 examples; up to 95% ee), and its use could be extended to diHydroxyacetone and protected Hydroxyacetones (7 examples; up to 90% ee). The high activity depicted by the catalyst has allowed its implementation in continuous flow. Under this operation mode, the supported threonine catalyst produces anti-Mannich adducts with generally higher diastereo- and enantioselectivity than in batch. A family of five different enantioenriched anti-Mannich adducts has been sequentially prepared in flow by passing different combinations of anilines and aromatic aldehydes over the same sample of catalyst. This confirms the suitability of this methodology for the rapid access to small libraries...
