The Experts below are selected from a list of 176151 Experts worldwide ranked by ideXlab platform
Richard M Lambert - One of the best experts on this subject based on the ideXlab platform.
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fundamental aspects of enantioselective heterogeneous catalysis a nexafs study of methyl pyruvate and s 1 1 naphthyl ethylamine on pt 1 1 1
Surface Science, 2001Co-Authors: Jonathan M Bonello, Federico J Williams, And Ashok K Santra, E C H Sykes, R Lindsay, Richard M LambertAbstract:Abstract Near-edge X-ray absorption fine structure (NEXAFS) and X-ray photoelectron spectroscopy have been used to characterise the adsorption and reactivity of methyl pyruvate and ( S )-(−)-1-(1-napthyl) ethylamine (( S )-NEA) on Pt{1 1 1}. Methyl pyruvate polymerises at room temperature yielding chains that contain CO bonds and no CC bonds; the CO bonds are inclined at 64±5° with respect to the metal surface. Polymerisation probably occurs by an aldol condensation that involves elimination of methanol. This mechanism is in excellent accord with the intramolecular bonding deduced from the NEXAFS results. These findings suggest that irreversible deactivation during start-up or steady state operation of Pt catalysts during enantioselective hydrogenation of alkyl Pyruvates can be due to hydrogen starvation, which results in polymerisation of the prochiral reactant. For ( S )-NEA, the naphthalene ring is inclined at 46±5° with respect to the metal surface. It is proposed that ( S )-NEA binds to the surface via contributions from both the aromatic π-system and the lone pair of electrons on the amine nitrogen atom.
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Fundamental aspects of enantioselective heterogeneous catalysis: a NEXAFS study of methyl pyruvate and (S)-(−)-1-(1-naphthyl) ethylamine on Pt{1 1 1}
Surface Science, 2001Co-Authors: Jonathan M Bonello, Federico J Williams, And Ashok K Santra, E C H Sykes, R Lindsay, Richard M LambertAbstract:Abstract Near-edge X-ray absorption fine structure (NEXAFS) and X-ray photoelectron spectroscopy have been used to characterise the adsorption and reactivity of methyl pyruvate and ( S )-(−)-1-(1-napthyl) ethylamine (( S )-NEA) on Pt{1 1 1}. Methyl pyruvate polymerises at room temperature yielding chains that contain CO bonds and no CC bonds; the CO bonds are inclined at 64±5° with respect to the metal surface. Polymerisation probably occurs by an aldol condensation that involves elimination of methanol. This mechanism is in excellent accord with the intramolecular bonding deduced from the NEXAFS results. These findings suggest that irreversible deactivation during start-up or steady state operation of Pt catalysts during enantioselective hydrogenation of alkyl Pyruvates can be due to hydrogen starvation, which results in polymerisation of the prochiral reactant. For ( S )-NEA, the naphthalene ring is inclined at 46±5° with respect to the metal surface. It is proposed that ( S )-NEA binds to the surface via contributions from both the aromatic π-system and the lone pair of electrons on the amine nitrogen atom.
John Kurhanewicz - One of the best experts on this subject based on the ideXlab platform.
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use of hyperpolarized 1 13c pyruvate and 2 13c pyruvate to probe the effects of the anticancer agent dichloroacetate on mitochondrial metabolism in vivo in the normal rat
Magnetic Resonance Imaging, 2012Co-Authors: Hikari A I Yoshihara, Robert Bok, John Kurhanewicz, Jenny Zhou, Minhua Zhu, Daniel B VigneronAbstract:Abstract Development of hyperpolarized technology utilizing dynamic nuclear polarization has enabled the measurement of 13 C metabolism in vivo at very high signal-to-noise ratio (SNR). In vivo mitochondrial metabolism can, in principle, be monitored with pyruvate, which is catalyzed to acetyl-CoA via pyruvate dehydrogenase (PDH). The purpose of this work was to determine whether the compound sodium dichloroacetate (DCA) could aid the study of mitochondrial metabolism with hyperpolarized pyruvate. DCA stimulates PDH by inhibiting its inhibitor, pyruvate dehydrogenase kinase. In this work, hyperpolarized [1- 13 C]pyruvate and [2- 13 C]pyruvate were used to probe mitochondrial metabolism in normal rats. Increased conversion to bicarbonate (+ 181±69%, P =.025) was measured when [1- 13 C]pyruvate was injected after DCA administration, and increased glutamate (+ 74±23%, P =.004), acetoacetate (+ 504±281%, P =.009) and acetylcarnitine (+ 377±157%, P =.003) were detected when [2- 13 C]pyruvate was used.
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metabolic imaging in the anesthetized rat brain using hyperpolarized 1 13c pyruvate and 1 13c ethyl pyruvate
Magnetic Resonance in Medicine, 2010Co-Authors: Ralph E Hurd, Yifen Yen, Dirk Mayer, Albert P Chen, David M Wilson, Susan J Kohler, Robert Bok, Daniel B Vigneron, John KurhanewiczAbstract:Abstract Formulation, polarization, and dissolution conditions were developed to obtain a stablehyperpolarized solution of [1- 13 C]-ethyl pyruvate. A maximum tolerated concentration andinjection rate were determined, and 13 C spectroscopic imaging was used to compare the uptake ofhyperpolarized [1- 13 C]-ethyl pyruvate relative to hyperpolarized [1- 13 C]-pyruvate intoanesthetized rat brain. Hyperpolarized [1- 13 C]-ethyl pyruvate and [1- 13 C]-pyruvate metabolicimaging in normal brain is demonstrated and quantified in this feasibility and range-finding study. Keywords hyperpolarized; carbon-13; ethyl-pyruvate; brain; pyruvate; lactateMR metabolic imaging of hyperpolarized [1- 13 C]-pyruvate has proven to be useful,especially in oncology and cardiology (1,2). Dynamic and tissue level changes in [1- 13 C]-pyruvate and its metabolic products, [1- 13 C]-lactate, [1- 13 C]-alanine, and [ 13 C] bicarbonate,have been shown to correlate with metabolic states of interest, including disease progression(3,4) and response to therapy (5,6). However, for potential neurologic applications, theblood-brain transport of pyruvate may be a limiting factor. Age, anesthesia, and dietary statecan all impact transport rates (7–9), and under some conditions, the 1- to 2-min window ofuseful hyperpolarized [1-
Jonathan M Bonello - One of the best experts on this subject based on the ideXlab platform.
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fundamental aspects of enantioselective heterogeneous catalysis a nexafs study of methyl pyruvate and s 1 1 naphthyl ethylamine on pt 1 1 1
Surface Science, 2001Co-Authors: Jonathan M Bonello, Federico J Williams, And Ashok K Santra, E C H Sykes, R Lindsay, Richard M LambertAbstract:Abstract Near-edge X-ray absorption fine structure (NEXAFS) and X-ray photoelectron spectroscopy have been used to characterise the adsorption and reactivity of methyl pyruvate and ( S )-(−)-1-(1-napthyl) ethylamine (( S )-NEA) on Pt{1 1 1}. Methyl pyruvate polymerises at room temperature yielding chains that contain CO bonds and no CC bonds; the CO bonds are inclined at 64±5° with respect to the metal surface. Polymerisation probably occurs by an aldol condensation that involves elimination of methanol. This mechanism is in excellent accord with the intramolecular bonding deduced from the NEXAFS results. These findings suggest that irreversible deactivation during start-up or steady state operation of Pt catalysts during enantioselective hydrogenation of alkyl Pyruvates can be due to hydrogen starvation, which results in polymerisation of the prochiral reactant. For ( S )-NEA, the naphthalene ring is inclined at 46±5° with respect to the metal surface. It is proposed that ( S )-NEA binds to the surface via contributions from both the aromatic π-system and the lone pair of electrons on the amine nitrogen atom.
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Fundamental aspects of enantioselective heterogeneous catalysis: a NEXAFS study of methyl pyruvate and (S)-(−)-1-(1-naphthyl) ethylamine on Pt{1 1 1}
Surface Science, 2001Co-Authors: Jonathan M Bonello, Federico J Williams, And Ashok K Santra, E C H Sykes, R Lindsay, Richard M LambertAbstract:Abstract Near-edge X-ray absorption fine structure (NEXAFS) and X-ray photoelectron spectroscopy have been used to characterise the adsorption and reactivity of methyl pyruvate and ( S )-(−)-1-(1-napthyl) ethylamine (( S )-NEA) on Pt{1 1 1}. Methyl pyruvate polymerises at room temperature yielding chains that contain CO bonds and no CC bonds; the CO bonds are inclined at 64±5° with respect to the metal surface. Polymerisation probably occurs by an aldol condensation that involves elimination of methanol. This mechanism is in excellent accord with the intramolecular bonding deduced from the NEXAFS results. These findings suggest that irreversible deactivation during start-up or steady state operation of Pt catalysts during enantioselective hydrogenation of alkyl Pyruvates can be due to hydrogen starvation, which results in polymerisation of the prochiral reactant. For ( S )-NEA, the naphthalene ring is inclined at 46±5° with respect to the metal surface. It is proposed that ( S )-NEA binds to the surface via contributions from both the aromatic π-system and the lone pair of electrons on the amine nitrogen atom.
Daniel B Vigneron - One of the best experts on this subject based on the ideXlab platform.
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use of hyperpolarized 1 13c pyruvate and 2 13c pyruvate to probe the effects of the anticancer agent dichloroacetate on mitochondrial metabolism in vivo in the normal rat
Magnetic Resonance Imaging, 2012Co-Authors: Hikari A I Yoshihara, Robert Bok, John Kurhanewicz, Jenny Zhou, Minhua Zhu, Daniel B VigneronAbstract:Abstract Development of hyperpolarized technology utilizing dynamic nuclear polarization has enabled the measurement of 13 C metabolism in vivo at very high signal-to-noise ratio (SNR). In vivo mitochondrial metabolism can, in principle, be monitored with pyruvate, which is catalyzed to acetyl-CoA via pyruvate dehydrogenase (PDH). The purpose of this work was to determine whether the compound sodium dichloroacetate (DCA) could aid the study of mitochondrial metabolism with hyperpolarized pyruvate. DCA stimulates PDH by inhibiting its inhibitor, pyruvate dehydrogenase kinase. In this work, hyperpolarized [1- 13 C]pyruvate and [2- 13 C]pyruvate were used to probe mitochondrial metabolism in normal rats. Increased conversion to bicarbonate (+ 181±69%, P =.025) was measured when [1- 13 C]pyruvate was injected after DCA administration, and increased glutamate (+ 74±23%, P =.004), acetoacetate (+ 504±281%, P =.009) and acetylcarnitine (+ 377±157%, P =.003) were detected when [2- 13 C]pyruvate was used.
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metabolic imaging in the anesthetized rat brain using hyperpolarized 1 13c pyruvate and 1 13c ethyl pyruvate
Magnetic Resonance in Medicine, 2010Co-Authors: Ralph E Hurd, Yifen Yen, Dirk Mayer, Albert P Chen, David M Wilson, Susan J Kohler, Robert Bok, Daniel B Vigneron, John KurhanewiczAbstract:Abstract Formulation, polarization, and dissolution conditions were developed to obtain a stablehyperpolarized solution of [1- 13 C]-ethyl pyruvate. A maximum tolerated concentration andinjection rate were determined, and 13 C spectroscopic imaging was used to compare the uptake ofhyperpolarized [1- 13 C]-ethyl pyruvate relative to hyperpolarized [1- 13 C]-pyruvate intoanesthetized rat brain. Hyperpolarized [1- 13 C]-ethyl pyruvate and [1- 13 C]-pyruvate metabolicimaging in normal brain is demonstrated and quantified in this feasibility and range-finding study. Keywords hyperpolarized; carbon-13; ethyl-pyruvate; brain; pyruvate; lactateMR metabolic imaging of hyperpolarized [1- 13 C]-pyruvate has proven to be useful,especially in oncology and cardiology (1,2). Dynamic and tissue level changes in [1- 13 C]-pyruvate and its metabolic products, [1- 13 C]-lactate, [1- 13 C]-alanine, and [ 13 C] bicarbonate,have been shown to correlate with metabolic states of interest, including disease progression(3,4) and response to therapy (5,6). However, for potential neurologic applications, theblood-brain transport of pyruvate may be a limiting factor. Age, anesthesia, and dietary statecan all impact transport rates (7–9), and under some conditions, the 1- to 2-min window ofuseful hyperpolarized [1-
Eduard Y. Chekmenev - One of the best experts on this subject based on the ideXlab platform.
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synthesis of unsaturated precursors for parahydrogen induced polarization and molecular imaging of 1 13c acetates and 1 13c Pyruvates via side arm hydrogenation
ACS Omega, 2018Co-Authors: Nikita V. Chukanov, Oleg G. Salnikov, Roman V. Shchepin, Kirill V. Kovtunov, Igor V. Koptyug, Eduard Y. ChekmenevAbstract:Hyperpolarized forms of 1-13C-acetates and 1-13C-Pyruvates are used as diagnostic contrast agents for molecular imaging of many diseases and disorders. Here, we report the synthetic preparation of 1-13C isotopically enriched and pure from solvent acetates and Pyruvates derivatized with unsaturated ester moiety. The reported unsaturated precursors can be employed for NMR hyperpolarization of 1-13C-acetates and 1-13C-Pyruvates via parahydrogen-induced polarization (PHIP). In this PHIP variant, Side arm hydrogenation (SAH) of unsaturated ester moiety is followed by the polarization transfer from nascent parahydrogen protons to 13C nucleus via magnetic field cycling procedure to achieve hyperpolarization of 13C nuclear spins. This work reports the synthesis of PHIP-SAH precursors: vinyl 1-13C-acetate (55% yield), allyl 1-13C-acetate (70% yield), propargyl 1-13C-acetate (45% yield), allyl 1-13C-pyruvate (60% yield), and propargyl 1-13C-pyruvate (35% yield). Feasibility of PHIP-SAH 13C hyperpolarization was ver...
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Synthesis of Unsaturated Precursors for Parahydrogen-Induced Polarization and Molecular Imaging of 1-13C‑Acetates and 1-13C‑Pyruvates via Side Arm Hydrogenation
2018Co-Authors: Nikita V. Chukanov, Oleg G. Salnikov, Roman V. Shchepin, Kirill V. Kovtunov, Igor V. Koptyug, Eduard Y. ChekmenevAbstract:Hyperpolarized forms of 1-13C-acetates and 1-13C-Pyruvates are used as diagnostic contrast agents for molecular imaging of many diseases and disorders. Here, we report the synthetic preparation of 1-13C isotopically enriched and pure from solvent acetates and Pyruvates derivatized with unsaturated ester moiety. The reported unsaturated precursors can be employed for NMR hyperpolarization of 1-13C-acetates and 1-13C-Pyruvates via parahydrogen-induced polarization (PHIP). In this PHIP variant, Side arm hydrogenation (SAH) of unsaturated ester moiety is followed by the polarization transfer from nascent parahydrogen protons to 13C nucleus via magnetic field cycling procedure to achieve hyperpolarization of 13C nuclear spins. This work reports the synthesis of PHIP-SAH precursors: vinyl 1-13C-acetate (55% yield), allyl 1-13C-acetate (70% yield), propargyl 1-13C-acetate (45% yield), allyl 1-13C-pyruvate (60% yield), and propargyl 1-13C-pyruvate (35% yield). Feasibility of PHIP-SAH 13C hyperpolarization was verified by 13C NMR spectroscopy: hyperpolarized allyl 1-13C-pyruvate was produced from propargyl 1-13C-pyruvate with 13C polarization of ∼3.2% in CD3OD and ∼0.7% in D2O. 13C magnetic resonance imaging is demonstrated with hyperpolarized 1-13C-pyruvate in aqueous medium
