29 research outputs found
Smashing mobile web development : going mobile with HTML5, CSS3, and Javascript / Greg Avola and Jon Raasch.
No full textIncludes index.computer bookfair2015xv, 296 pages :"By the time you finish this book, you'll possess all the knowledge and skills you need to create sophisticated mobile websites incorporating the features your users want, including geolocation, social media, and much more."-- Back cover
Identification of residues important for NAD+ binding by the Thermotoga maritima α-glucosidase AglA, a member of glycoside hydrolase family 4
No full textAbstractThe NAD+-requiring enzymes of glycoside hydrolase family 4 (GHF4) contain a region with a conserved Gly-XXX-Gly-Ser (GXGS) motif near their N-termini that is reminiscent of the fingerprint region of the Rossmann fold, a conserved structural motif of classical nicotinamide nucleotide-binding proteins. The function of this putative NAD+-binding motif in the α-glucosidase AglA of Thermotoga maritima was probed by directed mutagenesis. The Kd for NAD+ of the AglA mutants G10A, G12A and S13A was increased by about 300-, 5-, and 9-fold, respectively, while their Km for p-nitrophenyl-α-glucopyranoside was not seriously affected. The results indicate that the GXGS motif is indeed important for NAD+ binding by the glycosidases of GHF4
Essays on the Management of Servitization
No full textDas klassische Kerngeschäft vieler produzierender Unternehmen verändert sich zu Gunsten der Entwicklung digitaler und branchenübergreifender Produkt-Service-Systeme (PSS). Neben vielfältigen Chancen führt die Entwicklung von PSS zu Veränderungen auf mehreren Ebenen innerhalb des Unternehmens. Diese betreffen sowohl interne Organisationsstrukturen und damit die Anpassung etablierter Geschäftsmodelle und Unternehmensstrategien, als auch externe Faktoren, wie beispielsweise die gemeinsame Entwicklung von PSS mit externen Partnern in sogenannten Business Ökosystemen. Obwohl dieser als Servitization bezeichnete transformative Prozess der Wertschöpfung hin zu einer verstärkten Dienstleistungsorientierung auch in der betriebswirtschaftlichen Managementforschung zunehmend an Bedeutung gewinnt, ist der wissenschaftliche Diskurs über den Servitization-Prozess und dessen zugrundeliegenden Barrieren noch stark fragmentiert. Die vorliegende Dissertation beschreibt einen wissenschaftlich fundierten Weg zur Identifikation relevanter Barrieren, den daraus resultierenden Konsequenzen und notwendigen Fähigkeiten für das Management des Servitization-Prozesses. Die Arbeit setzt sich aus fünf Artikeln zusammen, die die zentrale Relevanz der systematischen Gestaltung des Servitization-Prozesses zeigen
Molecular, biochemical and structural analysis of amylolytic enzymes of Thermotoga maritima MSB8
No full textDas hyperthermophile Bakterium Thermotoga maritima MSB8 (Wachstumsbereich: 55°C - 90°C) ist eines der thermophilsten und ursprünglichsten aller bisher bekannten Mikroorganismen und verwertet durch einen fermentativen Stoffwechsel organische Polymere wie z.B. Stärke. An diesem Prozeß sind thermostabile Enzyme wie Glucosidasen und Maltodextrin Glycosyltransferasen beteiligt. AglA ist das erste Beispiel einer Maltodextrin umsetzenden alpha-Glucosidase mit einer ungewöhnlichen Abhängigkeit der enzymatischen Aktivität von einem Pyridinnukleotid-Kofaktor, Mn2+ und reduzierenden Bedingungen. Durch Gelfiltrationsstudien konnte gezeigt werden, daß das native AglA als Homodimer aus zwei identischen 55 kDa Untereinheiten vorliegt. Dabei spielt die An- oder Abwesenheit der genannten aktivierenden Komponenten für die Dimerisierung keine Rolle. Zur Klärung der Funktion konservierter Aminosäurereste wurden ortsspezifische Mutagenesestudien durchgeführt. Die extrem thermostabile nicht-hydrolytische Transferase MTase ist ebenfalls ein Homodimer. Die Transferaktivität des Enzyms ist streng auf die Übertragung von Maltosyleinheiten beschränkt. In Kooperation mit einer anderen Arbeitsgruppe gelang die Kristallstrukturaufklärung der MTase (MTase-Maltose-Komplex) mit einer Auflösung von 2,4 Å (2,1 Å). Die katalytische Kerndomäne enthält die typische ''TIM-barrel''-Struktur der Glycosylhydrolase Familie 13 mit dem aktiven Zentrum (katalytische Reste: Asp385, Glu414 und Asp468) am C-terminalen Ende des ''barrels''. Die Struktur ergab zwei Maltose-Bindestellen: eine befindet sich im aktiven Zentrum und definiert die ''subsites'' -2 und -1, die zweite liegt in einer Tasche in unmittelbarer Nachbarschaft zum aktiven Zentrum und könnte an der Erkennung verzweigter Substrate beteiligt sein. Die Röntgenstrukturanalyse der Maltosebindung liefert eine Erklärung für die einzigartige Transferspezifität des Enzyms. Durch gezielte ortsspezifische Mutagenesestudien konnten bisher weder die enzymatische Aktivität vollständig eliminiert, noch eine Modifizierung der spezifischen Transfereigenschaften erreicht werden. Es gelang jedoch eine Monomerisierung der MTase, wodurch die Thermoinaktivierungskinetik des Enzyms beschleunigt wurde. Neben den negativen Auswirkungen auf die Thermostabilisierung führte die Monomerisierung zu einem gesteigerten Hydrolyse/Transfer-Verhältnis im Vergleich zur Wildtyp-MTase.One of the most thermophilic and ancient bacteria known to date, the hyperthermophilic Thermotoga maritima MSB8 (growth range: 55°C - 90°C), degrades and fermentatively utilizes organic compounds like starch. Among thermostable enzymes involved in this process are glucosidases and maltodextrin glycosyltransferases. AglA represents the first example of a maltodextrin-degrading alpha-glucosidase with the unusual property of requiring a pyridine nucleotide cofactor, Mn2+ and reducing conditions for full activity. Using gel permeation chromatography the enzyme acted as a dimer (two identical 55 kDa subunits), irrespective of the presence or absence of the mentioned activating components. Point mutations were introduced to probe the role of conserved amino acid residues. The extremely thermostable, non-hydrolytic transferase MTase is also a homodimer and has a unique transfer specificity for maltosyl units. In cooperation with others, the crystal structure of MTase and its complex with maltose have been determined at 2.4 and 2.1 Å resolution, respectively. The catalytic core domain has the typical ''TIM-barrel'' structure of the glycosyl hydrolase family 13 with an active site cleft including the three proposed catalytic residues Asp385, Glu414 and Asp468 at the C-terminal end of the barrel. The structure revealed two maltose binding sites: one lies in the active site cleft defining subsites -2 and -1, the second is found in a pocket neighbouring the active site and could be involved in the recognition of branched substrates. The X-ray analysis of the binding mode of maltose provides an explanation for the strict transfer specificity of the enzyme. So far, it was not possible to eliminate the enzymatic activity completely or to modify the unique reaction chemistry by in vitro site-directed mutagenesis. On the other hand, monomerisation of MTase was achieved, which leads to the acceleration of the enzyme's thermoinactivation kinetics. In addition to negative influences on thermostabilisation the monomerisation leads to an increased ratio of hydrolysis / transglycosylation in comparison with the wild-type MTase
Crystal structure of Thermotoga maritima 4-alpha-glucanotransferase and its acarbose complex: implications for substrate specificity and catalysis
No full text4-α-Glucanotransferase (GTase) is an essential enzyme in α-1,4-glucan metabolism in bacteria and plants. It catalyses the transfer of malto-oligosaccharides from an 1,4-α-D-glucan molecule to the 4-hydroxyl group of an acceptor sugar molecule. The crystal structures of Thermotoga maritima GTase and its complex with the inhibitor acarbose have been determined at 2.6 Å and 2.5 Å resolution, respectively. The GTase structure consists of three domains, an N-terminal domain with the (β/α)δ barrel topology (domain A), a 65 residue domain, domain B, inserted between strand β3 and helix α6 of the barrel, and a C-terminal domain, domain C, which forms an antiparallel β-structure. Analysis of the complex of GTase with acarbose has revealed the locations of five sugar-binding subsites (-2 to +3) in the active-site cleft lying between domain B and the C-terminal end of the (β/α)δ barrel. The structure of GTase closely resembles the family 13 glycoside hydrolases and conservation of key catalytic residues previously identified for this family is consistent with a double-displacement catalytic mechanism for this enzyme. A distinguishing feature of GTase is a pair of tryptophan residues, W131 and W218, which, upon the carbohydrate inhibitor binding, form a remarkable aromatic "clamp" that captures the sugar rings at the acceptor-binding sites +1 and +2. Analysis of the structure of the complex shows that sugar residues occupying subsites from -2 to +2 engage in extensive interactions with the protein, whereas the +3 glucosyl residue makes relatively few contacts with the enzyme. Thus, the structure suggests that four subsites, from -2 to +2, play the dominant role in enzyme-substrate recognition, consistent with the observation that the smallest donor for T. maritima GTase is maltotetraose, the smallest chain transferred is a maltosyl unit and that the smallest residual fragment after transfer is maltose. A close similarity between the structures of GTase and oligo-1,6-glucosidase has allowed the structural features that determine differences in substrate specificity of these two enzymes to be analysed. © 2002 Elsevier Science Ltd. All rights reserved
The crystal structure of Thermotoga maritima maltosyltransferase and its implications for the molecular basis of the novel transfer specificity
No full textMaltosyltransferase (MTase) from the hyperthermophile Thermotoga maritima represents a novel maltodextrin glycosyltransferase acting on starch and malto-oligosaccharides. It catalyzes the transfer of maltosyl units from α-1,4-linked glucans or malto-oligosaccharides to other α-1,4-linked glucans, malto-oligosaccharides or glucose. It belongs to the glycoside hydrolase family 13, which represents a large group of (β/α)8 barrel proteins sharing a similar active site structure. The crystal structures of MTase and its complex with maltose have been determined at 2.4 Å and 2.1 Å resolution, respectively. MTase is a homodimer, each subunit of which consists of four domains, two of which are structurally homologous to those of other family 13 enzymes. The catalytic core domain has the (β/α)8 barrel fold with the active-site cleft formed at the C-terminal end of the barrel. Substrate binding experiments have led to the location of two distinct maltose-binding sites; one lies in the active-site cleft, covering subsites -2 and -1; the other is located in a pocket adjacent to the active-site cleft. The structure of MTase, together with the conservation of active-site residues among family 13 glycoside hydrolases, are consistent with a common double-displacement catalytic mechanism for this enzyme. Analysis of maltose binding in the active site reveals that the transfer of dextrinyl residues longer than a maltosyl unit is prevented by termination of the active-site cleft after the -2 subsite by the side-chain of Lys151 and the stretch of residues 314-317, providing an explanation for the strict transfer specificity of MTase. © 2001 Academic Press
Sprachvermittlung in der Verantwortung der Volkshochschulen: eine Herausforderung an die fachdidaktische Qualität des Sprachunterrichts
No full textFachdidaktische Qualität ist eine entscheidende Voraussetzung dafür, dass alle Bürgerinnen und Bürger der Europäischen Union multilinguale Kompetenz aufbauen können. Hierbei kommt insbesondere den Volkshochschulen die Aufgabe zu, ihre Kursleiter so aus- und fortzubilden, dass eine optimale fachdidaktische Unterrichtsgestaltung ermöglicht wird. Der Beitrag verdeutlicht, dass die Angewandte Linguistik und die Sprachlehrforschung hierzu wertvolle Impulse liefern. Der Autor plädiert darüber hinaus für eine am Lebenslangen Lernen orientierte Fachdidaktik. Dementsprechend wird das "Lehren des Lernens" als ein zentrales Ziel des Fremdsprachenunterrichts ausgewiesen.Didactical quality is a crucial precondition if all citizens of the European Union are to be able to develop multilingual skills. Here it is in particular adult education centres which have the task of training their teachers and offering them continuing education so as to make possible optimum didactical classroom instruction. This article shows that applied linguistics and research on teaching languages can provide an important impetus here. The author moreover issues a plea for specialised didactics oriented towards lifelong learning. "Learning teaching" is accordingly identified as a key objective of instruction in foreign languages
Testing of Shell Elements using Challenging Benchmark Problems
No full textThis paper presents the author’s experiences with testing the accuracy and convergence capability of the shell elements available in commercial software SAP2000 Ver. 11.0.0 and a variant of shell element developed by the author, namely the Kriging-based curved triangular shell element (K-Shell). A set of shell benchmark problems were utilized in the tests and two of them were selected here due to its difficulty in achieving a converged solution, i.e. the pinched cylinder with end diaphragms and the Raasch challenge problem. The performance of SAP2000 and the K-Shell elements were highlighted and compared to several shell elements from literature. The results showed that the convergence of the elements was relatively slow in the pinched cylinder problem and different shell elements converged to slightly different values in the Raasch challenge problem. The lesson learned is that a user of commercial finite element software must be cautious regarding the accuracy of the computational results when using shell elements. For SAP2000 users using its shell elements, the use of a very fine mesh of the quadrilateral shell elements are recommended in engineering practice. The performance of the K-Shell can be improved if its formulation could eliminate the shear and membrane locking. Future research for the K-Shell, therefore, should be directed on developing a locking-free K-Shell
Crystallization and preliminary X-ray crystallographic studies on 4-α-glucanotransferase fromThermotoga maritima
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