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  • 1
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    Highly efficient molybdenum-based catalysts for enantioselective alkene metathesis (2008)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2008-11-18
    Description: Discovery of efficient catalysts is one of the most compelling objectives of modern chemistry. Chiral catalysts are in particularly high demand, as they facilitate synthesis of enantiomerically enriched small molecules that are critical to developments in medicine, biology and materials science. Especially noteworthy are catalysts that promote-with otherwise inaccessible efficiency and selectivity levels-reactions demonstrated to be of great utility in chemical synthesis. Here we report a class of chiral catalysts that initiate alkene metathesis with very high efficiency and enantioselectivity. Such attributes arise from structural fluxionality of the chiral catalysts and the central role that enhanced electronic factors have in the catalytic cycle. The new catalysts have a stereogenic metal centre and carry only monodentate ligands; the molybdenum-based complexes are prepared stereoselectively by a ligand exchange process involving an enantiomerically pure aryloxide, a class of ligands scarcely used in enantioselective catalysis. We demonstrate the application of the new catalysts in an enantioselective synthesis of the Aspidosperma alkaloid, quebrachamine, through an alkene metathesis reaction that cannot be promoted by any of the previously reported chiral catalysts.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2663850/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2663850/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Malcolmson, Steven J -- Meek, Simon J -- Sattely, Elizabeth S -- Schrock, Richard R -- Hoveyda, Amir H -- GM-59426/GM/NIGMS NIH HHS/ -- R01 GM059426/GM/NIGMS NIH HHS/ -- R01 GM059426-09/GM/NIGMS NIH HHS/ -- England -- Nature. 2008 Dec 18;456(7224):933-7. doi: 10.1038/nature07594. Epub 2008 Nov 16.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, Massachusetts 02467, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19011612" target="_blank"〉PubMed〈/a〉
    Keywords: Alkenes/*chemistry ; Aspidosperma/*chemistry ; Catalysis ; Indole Alkaloids/*chemical synthesis/chemistry ; Ligands ; Molecular Structure ; Molybdenum/*chemistry ; Stereoisomerism
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 2
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    A new cyanogenic metabolite in Arabidopsis required for inducible pathogen defence (2015)
    Nature Publishing Group (NPG)
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    Publication Date: 2015-09-10
    Description: Thousands of putative biosynthetic genes in Arabidopsis thaliana have no known function, which suggests that there are numerous molecules contributing to plant fitness that have not yet been discovered. Prime among these uncharacterized genes are cytochromes P450 upregulated in response to pathogens. Here we start with a single pathogen-induced P450 (ref. 5), CYP82C2, and use a combination of untargeted metabolomics and coexpression analysis to uncover the complete biosynthetic pathway to 4-hydroxyindole-3-carbonyl nitrile (4-OH-ICN), a previously unknown Arabidopsis metabolite. This metabolite harbours cyanogenic functionality that is unprecedented in plants and exceedingly rare in nature; furthermore, the aryl cyanohydrin intermediate in the 4-OH-ICN pathway reveals a latent capacity for cyanogenic glucoside biosynthesis in Arabidopsis. By expressing 4-OH-ICN biosynthetic enzymes in Saccharomyces cerevisiae and Nicotiana benthamiana, we reconstitute the complete pathway in vitro and in vivo and validate the functions of its enzymes. Arabidopsis 4-OH-ICN pathway mutants show increased susceptibility to the bacterial pathogen Pseudomonas syringae, consistent with a role in inducible pathogen defence. Arabidopsis has been the pre-eminent model system for studying the role of small molecules in plant innate immunity; our results uncover a new branch of indole metabolism distinct from the canonical camalexin pathway, and support a role for this pathway in the Arabidopsis defence response. These results establish a more complete framework for understanding how the model plant Arabidopsis uses small molecules in pathogen defence.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4629851/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4629851/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Rajniak, Jakub -- Barco, Brenden -- Clay, Nicole K -- Sattely, Elizabeth S -- DP2 AT008321/AT/NCCIH NIH HHS/ -- R00 GM089985/GM/NIGMS NIH HHS/ -- R01 GM048707/GM/NIGMS NIH HHS/ -- R37 GM 48707/GM/NIGMS NIH HHS/ -- R37 GM048707/GM/NIGMS NIH HHS/ -- T32 GM007499/GM/NIGMS NIH HHS/ -- T32 GM007499-38/GM/NIGMS NIH HHS/ -- T32 GM008412-20/GM/NIGMS NIH HHS/ -- England -- Nature. 2015 Sep 17;525(7569):376-9. doi: 10.1038/nature14907. Epub 2015 Sep 9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemical Engineering, Stanford University, Stanford, California 94305, USA. ; Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06511, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26352477" target="_blank"〉PubMed〈/a〉
    Keywords: Arabidopsis/genetics/immunology/*metabolism/*microbiology ; Arabidopsis Proteins/metabolism ; Biosynthetic Pathways/genetics ; Cytochrome P-450 Enzyme System/metabolism ; Gene Expression Regulation, Plant ; Glucosides/biosynthesis ; Immunity, Innate/genetics/immunology ; Indoles/*metabolism ; Metabolomics ; Nitriles/*metabolism ; Plant Diseases/genetics/immunology/*microbiology ; Plant Immunity/genetics/*immunology ; Pseudomonas syringae/*immunology/*pathogenicity ; Saccharomyces cerevisiae/genetics ; Secondary Metabolism ; Thiazoles/metabolism ; Tobacco/genetics ; Transcriptome ; Virulence
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 3
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    Six enzymes from mayapple that complete the biosynthetic pathway to the etoposide aglycone (2015)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2015-09-12
    Description: Podophyllotoxin is the natural product precursor of the chemotherapeutic etoposide, yet only part of its biosynthetic pathway is known. We used transcriptome mining in Podophyllum hexandrum (mayapple) to identify biosynthetic genes in the podophyllotoxin pathway. We selected 29 candidate genes to combinatorially express in Nicotiana benthamiana (tobacco) and identified six pathway enzymes, including an oxoglutarate-dependent dioxygenase that closes the core cyclohexane ring of the aryltetralin scaffold. By coexpressing 10 genes in tobacco-these 6 plus 4 previously discovered-we reconstitute the pathway to (-)-4'-desmethylepipodophyllotoxin (the etoposide aglycone), a naturally occurring lignan that is the immediate precursor of etoposide and, unlike podophyllotoxin, a potent topoisomerase inhibitor. Our results enable production of the etoposide aglycone in tobacco and circumvent the need for cultivation of mayapple and semisynthetic epimerization and demethylation of podophyllotoxin.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lau, Warren -- Sattely, Elizabeth S -- DP2 AT008321/AT/NCCIH NIH HHS/ -- R00 GM089985/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 2015 Sep 11;349(6253):1224-8. doi: 10.1126/science.aac7202.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemical Engineering, Stanford University, Stanford, CA 94305, USA. ; Department of Chemical Engineering, Stanford University, Stanford, CA 94305, USA. sattely@stanford.edu.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26359402" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Biosynthetic Pathways/genetics ; Etoposide/*metabolism ; Gene Expression Regulation, Enzymologic ; Gene Expression Regulation, Plant ; *Genetic Engineering ; Methylation ; Mixed Function Oxygenases/genetics/*metabolism ; Molecular Sequence Data ; Podophyllotoxin/*analogs & derivatives/biosynthesis/*metabolism ; Podophyllum peltatum/*enzymology/genetics ; Tobacco/genetics/*metabolism ; Topoisomerase Inhibitors/*metabolism ; Transcriptome
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 4
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    An engineered pathway for N-hydroxy-pipecolic acid synthesis enhances systemic acquired resistance in tomato (2019)
    The American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2019
    Description: 〈p〉Systemic acquired resistance (SAR) is a powerful immune response that triggers broad-spectrum disease resistance throughout a plant. In the model plant 〈i〉Arabidopsis thaliana〈/i〉, long-distance signaling and SAR activation in uninfected tissues occur without circulating immune cells and instead rely on the metabolite 〈i〉N-〈/i〉hydroxy-pipecolic acid (NHP). Engineering SAR in crop plants would enable external control of a plant’s ability to mount a global defense response upon sudden changes in the environment. Such a metabolite-engineering approach would require the molecular machinery for producing and responding to NHP in the crop plant. Here, we used heterologous expression in 〈i〉Nicotiana benthamiana〈/i〉 leaves to identify a minimal set of 〈i〉Arabidopsis〈/i〉 genes necessary for the biosynthesis of NHP. Local expression of these genes in tomato leaves triggered SAR in distal tissues in the absence of a pathogen, suggesting that the SAR trait can be engineered to enhance a plant’s endogenous ability to respond to pathogens. We also showed tomato produces endogenous NHP in response to a bacterial pathogen and that NHP is present across the plant kingdom, raising the possibility that an engineering strategy to enhance NHP-induced defenses could be possible in many crop plants.〈/p〉
    Print ISSN: 1945-0877
    Electronic ISSN: 1937-9145
    Topics: Biology , Medicine
    Published by The American Association for the Advancement of Science (AAAS)
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