The Experts below are selected from a list of 1098 Experts worldwide ranked by ideXlab platform
Masaharu Nakamura - One of the best experts on this subject based on the ideXlab platform.
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ono pincer ruthenium complex bound Norvaline for efficient catalytic oxidation of methoxybenzenes with hydrogen peroxide
Organic and Biomolecular Chemistry, 2016Co-Authors: Ryota Yoshida, Katsuhiro Isozaki, Tomoya Yokoi, Nobuhiro Yasuda, Koichiro Sadakane, Takahiro Iwamoto, Hikaru Takaya, Masaharu NakamuraAbstract:The enhanced catalytic activity of ruthenium complex-bound Norvaline Boc-L-[Ru]Nva-OMe 1, in which the ONO-pincer ruthenium complex Ru(pydc)(terpy) 2 is tethered to the α-side chain of Norvaline, has been demonstrated for the oxidation of methoxybenzenes to p-benzoquinones with a wide scope of substrates and unique chemoselectivity.
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pd complex bound amino acid based supramolecular gel catalyst for intramolecular addition cyclization of alkynoic acids in water
ChemInform, 2012Co-Authors: Kazuki Ogata, Katsuhiro Isozaki, Tomoya Yokoi, Hikaru Takaya, Daisuke Sasano, Hirofumi Seike, Masaharu NakamuraAbstract:A xerogel derived from the supramolecular gel of NHC-pincer Pd-complex-bound Norvaline shows high catalytic activity for the intramolecular addition-cyclization of alkynoic acid and phenol derivatives in water furnishing ene-lactones in good to excellent yields.
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pd complex bound amino acid based supramolecular gel catalyst for intramolecular addition cyclization of alkynoic acids in water
Chemistry Letters, 2012Co-Authors: Kazuki Ogata, Katsuhiro Isozaki, Tomoya Yokoi, Hikaru Takaya, Daisuke Sasano, Hirofumi Seike, Masaharu NakamuraAbstract:An NCN-pincer Pd-complex-bound Norvaline-based supramolecular gel showed efficient catalytic activities for the intramolecular addition–cyclization of alkynoic acid and phenol derivatives in water ...
Uwe Horn - One of the best experts on this subject based on the ideXlab platform.
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trace element associated reduction of norleucine and Norvaline accumulation during oxygen limitation in a recombinant escherichia coli fermentation
Microbial Cell Factories, 2013Co-Authors: Michael Biermann, Julia Linnemann, Uwe Knupfer, Sebastian Vollstadt, Bettina Bardl, Guido Seidel, Uwe HornAbstract:Background Norleucine and Norvaline belong to a group of non-canonical amino acids which are synthesized as byproducts in the branched chain amino acid metabolism of Escherichia coli. The earlier observed misincorporation of these rare amino acids into recombinant proteins has attracted increasing attention due to the rising use of protein based biopharmaceuticals in clinical application. Experimental data revealed pyruvate overflow inducing conditions, which typically occur in oxygen limited zones of large-scale fermentations as a major reason leading to Norvaline and norleucine synthesis during E. coli cultivation. Previous approaches to suppress misincorporation of norleucine and Norvaline considered growth media supplementation with the relevant canonical isostructural compounds, but no research was performed on the impact of the overflow metabolism related trace elements molybdenum, nickel and selenium. These elements form essential parts of the formate hydrogen lyase (FHL) metalloprotein complex, which is a key enzyme of anaerobic pyruvate metabolism in E. coli and could therefore represent a crucial connection to the pyruvate accumulation associated biosynthesis of rare amino acids.
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Simultaneous analysis of the non-canonical amino acids norleucine and Norvaline in biopharmaceutical-related fermentation processes by a new ultra-high performance liquid chromatography approach
Amino Acids, 2013Co-Authors: Michael Biermann, Julia Linnemann, Uwe Knupfer, Sebastian Vollstadt, Bettina Bardl, Guido Seidel, Uwe HornAbstract:In this study, a precise and reliable ultra-high performance liquid chromatography (UHPLC) method for the simultaneous determination of non-canonical (Norvaline and norleucine) and standard amino acids (aspartic acid, glutamic acid, serine, histidine, glycine, threonine, arginine, tyrosine, methionine, valine, phenylalanine, isoleucine, leucine) in biopharmaceutical-related fermentation processes was established. After pre-column derivatization with ortho -phthaldialdehyde and 2-mercaptoethanol, the derivatives were separated on a sub -2 μm particle C_18 reverse-phase column. Identification and quantification of amino acids were carried out by fluorescence detection. To test method feasibility on standard HPLC instruments, the assay was properly transferred to a core–shell particle C_18 reverse-phase column. The limits of detection showed excellent sensitivity by values from 0.06 to 0.17 pmol per injection and limits of quantification between 0.19 and 0.89 pmol. In the present study, the newly established UHPLC method was applied to a recombinant antibody Escherichia coli fermentation process for the analysis of total free amino acids. We were able to specifically detect and quantify the unfavorable amino acids in such complex samples. Since we observed trace amounts of Norvaline and norleucine during all fermentation phases, an obligatory process monitoring should be considered to improve quality of recombinant protein drugs in future.
Michael Biermann - One of the best experts on this subject based on the ideXlab platform.
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limitation in a recombinant Escherichia coli
2016Co-Authors: Michael Biermann, Julia Linnemann, Uwe Knupfer, Sebastian Vollstadt, Bettina Bardl, Guido SeidelAbstract:Full list of author information is available at the end of the articleConclusions: The formation of norleucine and Norvaline by recombinant E. coli during cultivation with provoked oxygen limitation and glucose excess can be reduced to levels at the detection limit by adding the trace elements molybdenum, selenium and nickel to the fermentation medium. Even under the metabolic burden during induction phase the physiologically available concentrations of non-canonical amino acids remained low. Since our results allow facile process changes that can be easily implemented to avoid the undesirable accumulation of norleucine and Norvaline, we consider this study highly interesting for improved process development in E. coli based recombinant drug production and the future development of possible mechanisms to reduce misincorporation events into protein based biopharmaceuticals
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trace element associated reduction of norleucine and Norvaline accumulation during oxygen limitation in a recombinant escherichia coli fermentation
Microbial Cell Factories, 2013Co-Authors: Michael Biermann, Julia Linnemann, Uwe Knupfer, Sebastian Vollstadt, Bettina Bardl, Guido Seidel, Uwe HornAbstract:Background Norleucine and Norvaline belong to a group of non-canonical amino acids which are synthesized as byproducts in the branched chain amino acid metabolism of Escherichia coli. The earlier observed misincorporation of these rare amino acids into recombinant proteins has attracted increasing attention due to the rising use of protein based biopharmaceuticals in clinical application. Experimental data revealed pyruvate overflow inducing conditions, which typically occur in oxygen limited zones of large-scale fermentations as a major reason leading to Norvaline and norleucine synthesis during E. coli cultivation. Previous approaches to suppress misincorporation of norleucine and Norvaline considered growth media supplementation with the relevant canonical isostructural compounds, but no research was performed on the impact of the overflow metabolism related trace elements molybdenum, nickel and selenium. These elements form essential parts of the formate hydrogen lyase (FHL) metalloprotein complex, which is a key enzyme of anaerobic pyruvate metabolism in E. coli and could therefore represent a crucial connection to the pyruvate accumulation associated biosynthesis of rare amino acids.
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Simultaneous analysis of the non-canonical amino acids norleucine and Norvaline in biopharmaceutical-related fermentation processes by a new ultra-high performance liquid chromatography approach
Amino Acids, 2013Co-Authors: Michael Biermann, Julia Linnemann, Uwe Knupfer, Sebastian Vollstadt, Bettina Bardl, Guido Seidel, Uwe HornAbstract:In this study, a precise and reliable ultra-high performance liquid chromatography (UHPLC) method for the simultaneous determination of non-canonical (Norvaline and norleucine) and standard amino acids (aspartic acid, glutamic acid, serine, histidine, glycine, threonine, arginine, tyrosine, methionine, valine, phenylalanine, isoleucine, leucine) in biopharmaceutical-related fermentation processes was established. After pre-column derivatization with ortho -phthaldialdehyde and 2-mercaptoethanol, the derivatives were separated on a sub -2 μm particle C_18 reverse-phase column. Identification and quantification of amino acids were carried out by fluorescence detection. To test method feasibility on standard HPLC instruments, the assay was properly transferred to a core–shell particle C_18 reverse-phase column. The limits of detection showed excellent sensitivity by values from 0.06 to 0.17 pmol per injection and limits of quantification between 0.19 and 0.89 pmol. In the present study, the newly established UHPLC method was applied to a recombinant antibody Escherichia coli fermentation process for the analysis of total free amino acids. We were able to specifically detect and quantify the unfavorable amino acids in such complex samples. Since we observed trace amounts of Norvaline and norleucine during all fermentation phases, an obligatory process monitoring should be considered to improve quality of recombinant protein drugs in future.
Katsuhiro Isozaki - One of the best experts on this subject based on the ideXlab platform.
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ono pincer ruthenium complex bound Norvaline for efficient catalytic oxidation of methoxybenzenes with hydrogen peroxide
Organic and Biomolecular Chemistry, 2016Co-Authors: Ryota Yoshida, Katsuhiro Isozaki, Tomoya Yokoi, Nobuhiro Yasuda, Koichiro Sadakane, Takahiro Iwamoto, Hikaru Takaya, Masaharu NakamuraAbstract:The enhanced catalytic activity of ruthenium complex-bound Norvaline Boc-L-[Ru]Nva-OMe 1, in which the ONO-pincer ruthenium complex Ru(pydc)(terpy) 2 is tethered to the α-side chain of Norvaline, has been demonstrated for the oxidation of methoxybenzenes to p-benzoquinones with a wide scope of substrates and unique chemoselectivity.
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pd complex bound amino acid based supramolecular gel catalyst for intramolecular addition cyclization of alkynoic acids in water
ChemInform, 2012Co-Authors: Kazuki Ogata, Katsuhiro Isozaki, Tomoya Yokoi, Hikaru Takaya, Daisuke Sasano, Hirofumi Seike, Masaharu NakamuraAbstract:A xerogel derived from the supramolecular gel of NHC-pincer Pd-complex-bound Norvaline shows high catalytic activity for the intramolecular addition-cyclization of alkynoic acid and phenol derivatives in water furnishing ene-lactones in good to excellent yields.
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pd complex bound amino acid based supramolecular gel catalyst for intramolecular addition cyclization of alkynoic acids in water
Chemistry Letters, 2012Co-Authors: Kazuki Ogata, Katsuhiro Isozaki, Tomoya Yokoi, Hikaru Takaya, Daisuke Sasano, Hirofumi Seike, Masaharu NakamuraAbstract:An NCN-pincer Pd-complex-bound Norvaline-based supramolecular gel showed efficient catalytic activities for the intramolecular addition–cyclization of alkynoic acid and phenol derivatives in water ...
Tomoya Yokoi - One of the best experts on this subject based on the ideXlab platform.
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ono pincer ruthenium complex bound Norvaline for efficient catalytic oxidation of methoxybenzenes with hydrogen peroxide
Organic and Biomolecular Chemistry, 2016Co-Authors: Ryota Yoshida, Katsuhiro Isozaki, Tomoya Yokoi, Nobuhiro Yasuda, Koichiro Sadakane, Takahiro Iwamoto, Hikaru Takaya, Masaharu NakamuraAbstract:The enhanced catalytic activity of ruthenium complex-bound Norvaline Boc-L-[Ru]Nva-OMe 1, in which the ONO-pincer ruthenium complex Ru(pydc)(terpy) 2 is tethered to the α-side chain of Norvaline, has been demonstrated for the oxidation of methoxybenzenes to p-benzoquinones with a wide scope of substrates and unique chemoselectivity.
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pd complex bound amino acid based supramolecular gel catalyst for intramolecular addition cyclization of alkynoic acids in water
ChemInform, 2012Co-Authors: Kazuki Ogata, Katsuhiro Isozaki, Tomoya Yokoi, Hikaru Takaya, Daisuke Sasano, Hirofumi Seike, Masaharu NakamuraAbstract:A xerogel derived from the supramolecular gel of NHC-pincer Pd-complex-bound Norvaline shows high catalytic activity for the intramolecular addition-cyclization of alkynoic acid and phenol derivatives in water furnishing ene-lactones in good to excellent yields.
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pd complex bound amino acid based supramolecular gel catalyst for intramolecular addition cyclization of alkynoic acids in water
Chemistry Letters, 2012Co-Authors: Kazuki Ogata, Katsuhiro Isozaki, Tomoya Yokoi, Hikaru Takaya, Daisuke Sasano, Hirofumi Seike, Masaharu NakamuraAbstract:An NCN-pincer Pd-complex-bound Norvaline-based supramolecular gel showed efficient catalytic activities for the intramolecular addition–cyclization of alkynoic acid and phenol derivatives in water ...