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  • 1
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    Observation of covalent intermediates in an enzyme mechanism at atomic resolution (2001)
    American Association for the Advancement of Science (AAAS)
    Details
    Publikationsdatum: 2001-10-13
    Beschreibung: In classical enzymology, intermediates and transition states in a catalytic mechanism are usually inferred from a series of biochemical experiments. Here, we derive an enzyme mechanism from true atomic-resolution x-ray structures of reaction intermediates. Two ultra-high resolution structures of wild-type and mutant d-2-deoxyribose-5-phosphate (DRP) aldolase complexes with DRP at 1.05 and 1.10 angstroms unambiguously identify the postulated covalent carbinolamine and Schiff base intermediates in the aldolase mechanism. In combination with site-directed mutagenesis and (1)H nuclear magnetic resonance, we can now propose how the heretofore elusive C-2 proton abstraction step and the overall stereochemical course are accomplished. A proton relay system appears to activate a conserved active-site water that functions as the critical mediator for proton transfer.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Heine, A -- DeSantis, G -- Luz, J G -- Mitchell, M -- Wong, C H -- Wilson, I A -- GM44154/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 2001 Oct 12;294(5541):369-74.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Molecular Biology, Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/11598300" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Aldehyde-Lyases/*chemistry/genetics/*metabolism ; Amino Acid Substitution ; Binding Sites ; Catalysis ; Chemistry, Physical ; Crystallization ; Crystallography, X-Ray ; Escherichia coli/enzymology ; Hydrogen Bonding ; Hydrogen-Ion Concentration ; Ligands ; Lysine/chemistry ; Models, Chemical ; Mutagenesis, Site-Directed ; Mutation ; Nuclear Magnetic Resonance, Biomolecular ; Physicochemical Phenomena ; Protein Conformation ; Protein Folding ; Protein Structure, Tertiary ; Protons ; Ribosemonophosphates/*chemistry/*metabolism ; Schiff Bases ; Water
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von American Association for the Advancement of Science (AAAS)
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
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    Deeply inverted electron-hole recombination in a luminescent antibody-stilbene complex (2008)
    American Association for the Advancement of Science (AAAS)
    Details
    Publikationsdatum: 2008-03-01
    Beschreibung: The blue-emissive antibody EP2-19G2 that has been elicited against trans-stilbene has unprecedented ability to produce bright luminescence and has been used as a biosensor in various applications. We show that the prolonged luminescence is not stilbene fluorescence. Instead, the emissive species is a charge-transfer excited complex of an anionic stilbene and a cationic, parallel pi-stacked tryptophan. Upon charge recombination, this complex generates exceptionally bright blue light. Complex formation is enabled by a deeply penetrating ligand-binding pocket, which in turn results from a noncanonical interface between the two variable domains of the antibody.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Debler, Erik W -- Kaufmann, Gunnar F -- Meijler, Michael M -- Heine, Andreas -- Mee, Jenny M -- Pljevaljcic, Goran -- Di Bilio, Angel J -- Schultz, Peter G -- Millar, David P -- Janda, Kim D -- Wilson, Ian A -- Gray, Harry B -- Lerner, Richard A -- DK19038/DK/NIDDK NIH HHS/ -- GM38273/GM/NIGMS NIH HHS/ -- GM56528/GM/NIGMS NIH HHS/ -- R01 GM038273/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 2008 Feb 29;319(5867):1232-5. doi: 10.1126/science.1153445.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Molecular Biology, Scripps Research Institute, La Jolla, CA 92037, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18309081" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Antibodies, Monoclonal/*chemistry/genetics/immunology ; Antigen-Antibody Complex ; Binding Sites, Antibody ; Crystallization ; Crystallography, X-Ray ; *Electrons ; Fluorescence ; Fluorescence Polarization ; Haptens/chemistry/immunology ; Hydrophobic and Hydrophilic Interactions ; Immunoglobulin Variable Region/*chemistry/immunology ; Ligands ; Luminescence ; Mutation ; Oxidation-Reduction ; Protein Structure, Tertiary ; Spectrometry, Fluorescence ; Spectrum Analysis ; Stilbenes/*chemistry/immunology ; Tryptophan/chemistry
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von American Association for the Advancement of Science (AAAS)
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
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    Vinylogous chain branching catalysed by a dedicated polyketide synthase module (2013)
    Nature Publishing Group (NPG)
    Details
    Publikationsdatum: 2013-09-21
    Beschreibung: Bacteria use modular polyketide synthases (PKSs) to assemble complex polyketides, many of which are leads for the development of clinical drugs, in particular anti-infectives and anti-tumoral agents. Because these multifarious compounds are notoriously difficult to synthesize, they are usually produced by microbial fermentation. During the past two decades, an impressive body of knowledge on modular PKSs has been gathered that not only provides detailed insight into the biosynthetic pathways but also allows the rational engineering of enzymatic processing lines to yield structural analogues. Notably, a hallmark of all PKS modules studied so far is the head-to-tail fusion of acyl and malonyl building blocks, which leads to linear backbones. Yet, structural diversity is limited by this uniform assembly mode. Here we demonstrate a new type of PKS module from the endofungal bacterium Burkholderia rhizoxinica that catalyses a Michael-type acetyl addition to generate a branch in the carbon chain. In vitro reconstitution of the entire PKS module, X-ray structures of a ketosynthase-branching didomain and mutagenesis experiments revealed a crucial role of the ketosynthase domain in branching the carbon chain. We present a trapped intermediary state in which acyl carrier protein and ketosynthase are covalently linked by the branched polyketide and suggest a new mechanism for chain alkylation, which is functionally distinct from terpenoid-like beta-branching. For the rice seedling blight toxin rhizoxin, one of the strongest known anti-mitotic agents, the non-canonical polyketide modification is indispensable for phytotoxic and anti-tumoral activities. We propose that the formation of related pharmacophoric groups follows the same general scheme and infer a unifying vinylogous branching reaction for PKS modules with a ketosynthase-branching-acyl-carrier-protein architecture. This study unveils the structure and function of a new PKS module that broadens the biosynthetic scope of polyketide biosynthesis and sets the stage for rationally creating structural diversity.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Bretschneider, Tom -- Heim, Joel B -- Heine, Daniel -- Winkler, Robert -- Busch, Benjamin -- Kusebauch, Bjorn -- Stehle, Thilo -- Zocher, Georg -- Hertweck, Christian -- England -- Nature. 2013 Oct 3;502(7469):124-8. doi: 10.1038/nature12588. Epub 2013 Sep 18.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biomolecular Chemistry, Leibniz Institute for Natural Product Research and Infection Biology (HKI), Jena 07745, Germany.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24048471" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Burkholderia/chemistry/*enzymology/genetics ; Catalysis ; Crystallography, X-Ray ; Lactones/metabolism ; Macrolides/chemistry ; *Models, Molecular ; Mutagenesis ; Polyketide Synthases/genetics/*metabolism ; Protein Structure, Tertiary
    Print ISSN: 0028-0836
    Digitale ISSN: 1476-4687
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von Nature Publishing Group (NPG)
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
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    Generated spiral bevel gears - Optimal machine-tool settings and tooth contact analysis (1985)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: Geometry and kinematic errors were studied for Gleason generated spiral bevel gears. A new method was devised for choosing optimal machine settings. These settings provide zero kinematic errors and an improved bearing contact. The kinematic errors are a major source of noise and vibration in spiral bevel gears. The improved bearing contact gives improved conditions for lubrication. A computer program for tooth contact analysis was developed, and thereby the new generation process was confirmed. The new process is governed by the requirement that during the generation process there is directional constancy of the common normal of the contacting surfaces for generator and generated surfaces of pinion and gear.
    Schlagwort(e): MECHANICAL ENGINEERING
    Materialart: SAE PAPER 851573
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 5
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    Determination of settings of a tilted head-cutter for generation of hypoid and spiral bevel gears (1988)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: Kinematics of Gleason mechanisms of hypoid and spiral bevel cutting machines are considered. These mechanisms are designated to install the position and tilt of the head cutter. The tilt of the head cutter with standard blades provides the required pressure angle. The authors have developed the matrix presentation of kinematics of these meachanisms and basic equations for the required settings. An example is presented based on the developed computation procedure.
    Schlagwort(e): MECHANICAL ENGINEERING
    Materialart: NASA-CR-182138 , NAS 1.26:182138 , AVSCOM-TR-88-C-016 , AD-A196985
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 6
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    Generated spiral bevel gears: Optimal machine-tool settings and tooth contact analysis (1985)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: Geometry and kinematic errors were studied for Gleason generated spiral bevel gears. A new method was devised for choosing optimal machine settings. These settings provide zero kinematic errors and an improved bearing contact. The kinematic errors are a major source of noise and vibration in spiral bevel gears. The improved bearing contact gives improved conditions for lubrication. A computer program for tooth contact analysis was developed, and thereby the new generation process was confirmed. The new process is governed by the requirement that during the generation process there is directional constancy of the common normal of the contacting surfaces for generator and generated surfaces of pinion and gear.
    Schlagwort(e): MECHANICAL ENGINEERING
    Materialart: NASA-TM-87075 , E-2648 , NAS 1.15:87075 , USAAVSCOM-TR-85-C-9
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 7
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    Method for generation of spiral bevel gears with conjugate gear tooth surfaces (1987)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: A method for generation of spiral bevel gears is proposed that provides conjugate gear tooth surfaces. This method is based on a new principle for the performance of parallel motion of a straight line that slides along two mating ellipses with related dimensions and parameters of orientation. The parallel motion of the straight line, that is, the contact normal, is performed parallel to the line which passes through the foci of symmetry of the related ellipses. The manufacturing of gears can be performed with the existing Gleason's equipment.
    Schlagwort(e): MECHANICAL ENGINEERING
    Materialart: ASME PAPER 86-DET-3 , ASME; 163-170
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 8
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    Braze alloy spreading on steel (1978)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: Scanning electron microscopy (SEM) and Auger electron microscopy (AEM) were employed to observe elemental surface decomposition resulting from the brazing of a copper-treated steel. Two types of steel were used for the study, stainless steel (treated with a eutectic silver-copper alloy), and low-carbon steel (treated with pure copper). Attention is given to oxygen partial pressure during the processes; a low enough pressure (8 x 10 to the -5th torr) was found to totally inhibit the spreading of the filler material at a fixed heating cycle. With both types of steel, copper treatment enhanced even spreading at a decreased temperature.
    Schlagwort(e): MECHANICAL ENGINEERING
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 9
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    Generation of spiral bevel gears with zero kinematical errors and computer aided tooth contact analysis (1986)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: Kinematic errors in spiral bevel gears are a major source of noise and vibrations in transmissions. A method for the generation of Gleason's spiral bevel gears which provides conjugated gear tooth surfaces and an improved bearing contact was developed. A computer program for the simulation of meshing, misalignment, and bearing contact was written.
    Schlagwort(e): MECHANICAL ENGINEERING
    Materialart: NASA-TM-87273 , E-2932 , NAS 1.15:87273 , USAAVSCOM-TR-86-C-2 , World Congress on Gearing; Mar 02, 1986 - Mar 05, 1986; Paris; France
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 10
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    Fossile Riesen-Eiskeilnetze am Niederrhein (2011)
    Geozon Science Media
    Details
    Publikationsdatum: 2021-03-29
    Beschreibung: Auf niederrheinischen Terrassenschottern finden sich in zum Teil regelmäßigen Abständen taschenförmige Gebilde mit einer durch Eisenoxyde und -hydroxyde auffällig gefärbten Füllung von Feinmaterial. Sie können bis zu 6 m breit werden und bis etwa 3 m in die Tiefe reichen. Bisher wurden sie als Würge- und Taschenböden gedeutet. Es wird gezeigt, daß diese Gebilde netzartig miteinander in Verbindung stehen und Zeugen fossiler Eiskeilnetze darstellen. Ihre Bildung erfolgte sehr wahrscheinlich nur während der Rißeiszeit im unmittelbaren Vorfeld des Inlandeises,
    Beschreibung: research
    Schlagwort(e): 551.7 ; VAR 000 ; Glazialgeologie ; terrassenschotter ; niederrhein ; geomorphologie ; würgeboden ; fossile ; riesen-eiskeilnetz ; taschenboden
    Sprache: Deutsch
    Materialart: article , publishedVersion
    Standort Signatur Erwartet Verfügbarkeit
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    CITATION GEO-LEO
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