The Experts below are selected from a list of 2394 Experts worldwide ranked by ideXlab platform

Rujin Huang - One of the best experts on this subject based on the ideXlab platform.

  • determination of Alkylamines in atmospheric aerosol particles a comparison of gas chromatography mass spectrometry and ion chromatography approaches
    Atmospheric Measurement Techniques, 2014
    Co-Authors: Rujin Huang, Kinfai Ho, Gehui Wang, W-b Li, Qiyuan Wang, Y.r. Wang, X. Chen
    Abstract:

    Abstract. In recent years low molecular weight Alkylamines have been recognized to play an important role in particle formation and growth in the lower atmosphere. However, major uncertainties are associated with their atmospheric processes, sources and sinks, mostly due to the lack of ambient measurements and the difficulties in accurate quantification of Alkylamines at trace level. In this study, we present the evaluation and optimization of two analytical approaches, i.e., gas chromatography–mass spectrometry (GC-MS) and ion chromatography (IC), for the determination of Alkylamines in aerosol particles. Alkylamines were converted to carbamates through derivatization with isobutyl chloroformate for GC-MS determination. A set of parameters affecting the analytical performances of the GC-MS approach, including reagent amount, reaction time and pH value, was evaluated and optimized. The accuracy is 84.3–99.1%, and the limits of detection obtained are 1.8–3.9 pg (or 0.02–0.04 ng m−3). For the IC approach, a solid-phase extraction (SPE) column was used to separate Alkylamines from interfering cations before IC analysis. 1–2% (v/v) of acetone (or 2–4% (v/v) of acetonitrile) was added to the eluent to improve the separation of Alkylamines on the IC column. The limits of detection obtained are 2.1–15.9 ng (or 0.9–6.4 ng m−3), and the accuracy is 55.1-103.4%. The lower accuracy can be attributed to evaporation losses of amines during the sample concentration procedure. Measurements of ambient aerosol particle samples collected in Hong Kong show that the GC-MS approach is superior to the IC approach for the quantification of primary and secondary Alkylamines due to its lower detection limits and higher accuracy.

Daniel Wiegmann - One of the best experts on this subject based on the ideXlab platform.

  • pyridoxal 5 phosphate dependent alkyl transfer in nucleoside antibiotic biosynthesis
    Nature Chemical Biology, 2020
    Co-Authors: Zheng Cui, Jonathan Overbay, Xiachang Wang, Xiaodong Liu, Yinan Zhang, Minakshi Bhardwaj, Anke Lemke, Daniel Wiegmann
    Abstract:

    Several nucleoside antibiotics are structurally characterized by a 5″-amino-5″-deoxyribose (ADR) appended via a glycosidic bond to a high-carbon sugar nucleoside (5′S,6′S)-5′-C-glycyluridine (GlyU). GlyU is further modified with an N-Alkylamine linker, the biosynthetic origin of which has yet to be established. By using a combination of feeding experiments with isotopically labeled precursors and characterization of recombinant proteins from multiple pathways, the biosynthetic mechanism for N-Alkylamine installation for ADR–GlyU-containing nucleoside antibiotics has been uncovered. The data reveal S-adenosyl-l-methionine (AdoMet) as the direct precursor of the N-Alkylamine, but, unlike conventional AdoMet- or decarboxylated AdoMet-dependent alkyltransferases, the reaction is catalyzed by a pyridoxal-5′-phosphate-dependent aminobutyryltransferase (ABTase) using a stepwise γ-replacement mechanism that couples γ-elimination of AdoMet with aza-γ-addition onto the disaccharide alkyl acceptor. In addition to using a conceptually different strategy for AdoMet-dependent alkylation, the newly discovered ABTases require a phosphorylated disaccharide alkyl acceptor, revealing a cryptic intermediate in the biosynthetic pathway. Rather than a typical S-adenosylmethionine-dependent alkyltransferase, the installation of the N-Alkylamine linker in several nucleoside antibiotics is catalyzed via γ-replacement by a pyridoxal-5′-phosphate-dependent aminobutyryltransferase.

  • pyridoxal 5 phosphate dependent alkyl transfer in nucleoside antibiotic biosynthesis
    Nature Chemical Biology, 2020
    Co-Authors: Zheng Cui, Jonathan Overbay, Xiachang Wang, Xiaodong Liu, Yinan Zhang, Minakshi Bhardwaj, Anke Lemke, Daniel Wiegmann
    Abstract:

    Several nucleoside antibiotics are structurally characterized by a 5″-amino-5″-deoxyribose (ADR) appended via a glycosidic bond to a high-carbon sugar nucleoside (5'S,6'S)-5'-C-glycyluridine (GlyU). GlyU is further modified with an N-Alkylamine linker, the biosynthetic origin of which has yet to be established. By using a combination of feeding experiments with isotopically labeled precursors and characterization of recombinant proteins from multiple pathways, the biosynthetic mechanism for N-Alkylamine installation for ADR-GlyU-containing nucleoside antibiotics has been uncovered. The data reveal S-adenosyl-L-methionine (AdoMet) as the direct precursor of the N-Alkylamine, but, unlike conventional AdoMet- or decarboxylated AdoMet-dependent alkyltransferases, the reaction is catalyzed by a pyridoxal-5'-phosphate-dependent aminobutyryltransferase (ABTase) using a stepwise γ-replacement mechanism that couples γ-elimination of AdoMet with aza-γ-addition onto the disaccharide alkyl acceptor. In addition to using a conceptually different strategy for AdoMet-dependent alkylation, the newly discovered ABTases require a phosphorylated disaccharide alkyl acceptor, revealing a cryptic intermediate in the biosynthetic pathway.

Xiachang Wang - One of the best experts on this subject based on the ideXlab platform.

  • pyridoxal 5 phosphate dependent alkyl transfer in nucleoside antibiotic biosynthesis
    Nature Chemical Biology, 2020
    Co-Authors: Zheng Cui, Jonathan Overbay, Xiachang Wang, Xiaodong Liu, Yinan Zhang, Minakshi Bhardwaj, Anke Lemke, Daniel Wiegmann
    Abstract:

    Several nucleoside antibiotics are structurally characterized by a 5″-amino-5″-deoxyribose (ADR) appended via a glycosidic bond to a high-carbon sugar nucleoside (5′S,6′S)-5′-C-glycyluridine (GlyU). GlyU is further modified with an N-Alkylamine linker, the biosynthetic origin of which has yet to be established. By using a combination of feeding experiments with isotopically labeled precursors and characterization of recombinant proteins from multiple pathways, the biosynthetic mechanism for N-Alkylamine installation for ADR–GlyU-containing nucleoside antibiotics has been uncovered. The data reveal S-adenosyl-l-methionine (AdoMet) as the direct precursor of the N-Alkylamine, but, unlike conventional AdoMet- or decarboxylated AdoMet-dependent alkyltransferases, the reaction is catalyzed by a pyridoxal-5′-phosphate-dependent aminobutyryltransferase (ABTase) using a stepwise γ-replacement mechanism that couples γ-elimination of AdoMet with aza-γ-addition onto the disaccharide alkyl acceptor. In addition to using a conceptually different strategy for AdoMet-dependent alkylation, the newly discovered ABTases require a phosphorylated disaccharide alkyl acceptor, revealing a cryptic intermediate in the biosynthetic pathway. Rather than a typical S-adenosylmethionine-dependent alkyltransferase, the installation of the N-Alkylamine linker in several nucleoside antibiotics is catalyzed via γ-replacement by a pyridoxal-5′-phosphate-dependent aminobutyryltransferase.

  • pyridoxal 5 phosphate dependent alkyl transfer in nucleoside antibiotic biosynthesis
    Nature Chemical Biology, 2020
    Co-Authors: Zheng Cui, Jonathan Overbay, Xiachang Wang, Xiaodong Liu, Yinan Zhang, Minakshi Bhardwaj, Anke Lemke, Daniel Wiegmann
    Abstract:

    Several nucleoside antibiotics are structurally characterized by a 5″-amino-5″-deoxyribose (ADR) appended via a glycosidic bond to a high-carbon sugar nucleoside (5'S,6'S)-5'-C-glycyluridine (GlyU). GlyU is further modified with an N-Alkylamine linker, the biosynthetic origin of which has yet to be established. By using a combination of feeding experiments with isotopically labeled precursors and characterization of recombinant proteins from multiple pathways, the biosynthetic mechanism for N-Alkylamine installation for ADR-GlyU-containing nucleoside antibiotics has been uncovered. The data reveal S-adenosyl-L-methionine (AdoMet) as the direct precursor of the N-Alkylamine, but, unlike conventional AdoMet- or decarboxylated AdoMet-dependent alkyltransferases, the reaction is catalyzed by a pyridoxal-5'-phosphate-dependent aminobutyryltransferase (ABTase) using a stepwise γ-replacement mechanism that couples γ-elimination of AdoMet with aza-γ-addition onto the disaccharide alkyl acceptor. In addition to using a conceptually different strategy for AdoMet-dependent alkylation, the newly discovered ABTases require a phosphorylated disaccharide alkyl acceptor, revealing a cryptic intermediate in the biosynthetic pathway.

Yinan Zhang - One of the best experts on this subject based on the ideXlab platform.

  • pyridoxal 5 phosphate dependent alkyl transfer in nucleoside antibiotic biosynthesis
    Nature Chemical Biology, 2020
    Co-Authors: Zheng Cui, Jonathan Overbay, Xiachang Wang, Xiaodong Liu, Yinan Zhang, Minakshi Bhardwaj, Anke Lemke, Daniel Wiegmann
    Abstract:

    Several nucleoside antibiotics are structurally characterized by a 5″-amino-5″-deoxyribose (ADR) appended via a glycosidic bond to a high-carbon sugar nucleoside (5′S,6′S)-5′-C-glycyluridine (GlyU). GlyU is further modified with an N-Alkylamine linker, the biosynthetic origin of which has yet to be established. By using a combination of feeding experiments with isotopically labeled precursors and characterization of recombinant proteins from multiple pathways, the biosynthetic mechanism for N-Alkylamine installation for ADR–GlyU-containing nucleoside antibiotics has been uncovered. The data reveal S-adenosyl-l-methionine (AdoMet) as the direct precursor of the N-Alkylamine, but, unlike conventional AdoMet- or decarboxylated AdoMet-dependent alkyltransferases, the reaction is catalyzed by a pyridoxal-5′-phosphate-dependent aminobutyryltransferase (ABTase) using a stepwise γ-replacement mechanism that couples γ-elimination of AdoMet with aza-γ-addition onto the disaccharide alkyl acceptor. In addition to using a conceptually different strategy for AdoMet-dependent alkylation, the newly discovered ABTases require a phosphorylated disaccharide alkyl acceptor, revealing a cryptic intermediate in the biosynthetic pathway. Rather than a typical S-adenosylmethionine-dependent alkyltransferase, the installation of the N-Alkylamine linker in several nucleoside antibiotics is catalyzed via γ-replacement by a pyridoxal-5′-phosphate-dependent aminobutyryltransferase.

  • pyridoxal 5 phosphate dependent alkyl transfer in nucleoside antibiotic biosynthesis
    Nature Chemical Biology, 2020
    Co-Authors: Zheng Cui, Jonathan Overbay, Xiachang Wang, Xiaodong Liu, Yinan Zhang, Minakshi Bhardwaj, Anke Lemke, Daniel Wiegmann
    Abstract:

    Several nucleoside antibiotics are structurally characterized by a 5″-amino-5″-deoxyribose (ADR) appended via a glycosidic bond to a high-carbon sugar nucleoside (5'S,6'S)-5'-C-glycyluridine (GlyU). GlyU is further modified with an N-Alkylamine linker, the biosynthetic origin of which has yet to be established. By using a combination of feeding experiments with isotopically labeled precursors and characterization of recombinant proteins from multiple pathways, the biosynthetic mechanism for N-Alkylamine installation for ADR-GlyU-containing nucleoside antibiotics has been uncovered. The data reveal S-adenosyl-L-methionine (AdoMet) as the direct precursor of the N-Alkylamine, but, unlike conventional AdoMet- or decarboxylated AdoMet-dependent alkyltransferases, the reaction is catalyzed by a pyridoxal-5'-phosphate-dependent aminobutyryltransferase (ABTase) using a stepwise γ-replacement mechanism that couples γ-elimination of AdoMet with aza-γ-addition onto the disaccharide alkyl acceptor. In addition to using a conceptually different strategy for AdoMet-dependent alkylation, the newly discovered ABTases require a phosphorylated disaccharide alkyl acceptor, revealing a cryptic intermediate in the biosynthetic pathway.

Adkins Nathan - One of the best experts on this subject based on the ideXlab platform.

  • Reactions of 2-chloro-3-methyl-1,4-naphthoquinone with Alkylamines
    OxyScholar, 2006
    Co-Authors: Adkins Nathan
    Abstract:

    The reactivity of 2-chloro-3-methyl-1,4-naphthoquinone with Alkylamines is studied here. In the reaction with Alkylamines, we found 2-bromo-3-methyl-1,4-naphthoquinone, an analog of 2-chloro-3-methyl-1,4-naphthqouinone, exclusively yielded 2- alkylamino-3-bromo-1,4-naphthoquinone through demethylation. Similarly as 2-bromo-3-methyl-1,4-naphthoquinone, 2-chloro-3-methyl-1,4-naphthoquinone in methanol yields 2-alkylamino-3-chloro-1,4-naphthoquinone as the major product with primary Alkylamines such as propylamine, isopropylamine, cyclopropylamine, ethylamine and methylamine through demethylation. Different from the reactions of 2-bromo-3-methyl-1,4-naphthoquinone, however, 2-chloro-3-methyl-1,4-naphthoquinone produces another product, 2-alkylamino-3-methyl-1,4-naphthoquinone, in which the primary amine substitutes for the chlorine. Since a halogen such as chlorine and bromine is a good leaving group, the substitution of the halogen was originally expected for both 2-chloro-3-methyl-1,4-naphthoquinone and 2-bromo-3-methyl-1,4-naphthqouinone with reactions with primary Alkylamine. The unusual demethylation reaction is caused by the acidic nature of the ?-proton of 2-halogeno-3-methyl-1,4-naphthoquinone. We studied the effect of the solvent, by systematically changing the polarity from water to hexane. In less polar solvent, the main product 2-alkylamino-3-chloro-1,4-naphthoquinone was yielded more favorably. We have also identified a new product while studying the solvent effect

  • Reactions of 2-chloro-3-methyl-1,4-naphthoquinone with Alkylamines
    OxyScholar, 2005
    Co-Authors: Adkins Nathan
    Abstract:

    The reactivity of 2-chloro-3-methyl-1,4-naphthoquinone with Alkylamines is studied here. In the reaction with Alkylamines, we found 2-bromo-3-methyl-1,4-naphthoquinone, an analog of 2-chloro-3-methyl-1,4-naphthqouinone, exclusively yielded 2- alkylamino-3-bromo-1,4-naphthoquinone through demethylation. Similarly as 2-bromo-3-methyl-1,4-naphthoquinone, 2-chloro-3-methyl-1,4-naphthoquinone in methanol yields 2-alkylamino-3-chloro-1,4-naphthoquinone as the major product with primary amines such as propylamine, isopropylamine, cyclopropylamine, ethylamine and methylamine through demethylation. Different from the reactions of 2-bromo-3-methyl-1,4-naphthoquinone, however, 2-chloro-3-methyl-1,4-naphthoquinone produces another product, 2-alkylamino-3-methyl-1,4-naphthoquinone, in which the primary amine substitutes for the chlorine. Since a halogen such as chlorine and bromine is a good leaving group, the substitution of the halogen was originally expected for both 2-chloro-3-methyl-1,4-naphthoquinone and 2-bromo-3-methyl-1,4-naphthqouinone with reactions with primary amine. The unusual demethylation reaction is caused by the acidic nature of theα-proton of 2-halogeno-3-methyl-1,4-naphthoquinone