1,721,159 research outputs found
Isotopologue profiles for the determination of metabolic pathways and flux in microorganisms and insects
No full textDie Aufklärung von Stoffwechselwegen in Mikroorganismen und Insekten anhand von Markierungsexperimenten mit Stabilisotopen ist z.B. für die Entwicklung neuer Medikamente gegen multiresistente, pathogene Mikroorganismen von großer Bedeutung. Mittels 13C-Kernresonanzspektroskopie (NMR) und Gaschromatographie/Massenspektrometrie (GC/MS) wurden Isotopologprofile bestimmt und zentrale Stoffwechselrouten unter physiologischen Bedingungen abgeleitet. Im Falle von Listeria monocytogenes wurde die metabole Interaktion mit Wirtszellen quantifiziert. Die Daten belegen, dass Isotopologmethoden neben der Bestimmung von metabolen Netzwerken auch zur Bestimmung der chemischen Kommunikation zwischen Organismen eingesetzt werden können.The elucidation of metabolic pathways in microorganisms and insects by means of stable isotope labelling experiments is of great importance e.g. for the development of new pharmaceuticals against multi-resistant pathogens. The isotopologue profiles were determined by 13C-nuclear magnetic resonance spectroscopy (NMR) und gas chromatography/mass spectrometry (GC/MS) and central metabolic routes under physiological conditions were derived. In the case of Listeria monocytogenes, the metabolic interaction with host cells was quantified. The data document that besides the analysis of metabolic networks, isotopologue methods can be used to identify chemical communication between organisms
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Studies on enzymes from biosynthesis of riboflavin
No full textLumazinsynthasen und Riboflavinsynthasen sind Enzyme des Riboflavinbiosyntheseweges in vielen Pflanzen und Mikroorganismen. Kern der Arbeit war die biochemische Charakterisierung dieser beiden Enzyme aus verschiedenen, zum Teil pathogenen Organismen. Im Rahmen dieser Arbeit konnten Kenntnisse über deren Quartärstrukturen sowie Reaktionsmechanismen gewonnen werden. Der Schwerpunkt lag hierbei auf Mutagenesestudien an Aminosäuren des aktiven Zentrums einer archaealen Riboflavinsynthase, welche mit eubakteriellen und pflanzlichen Riboflavinsynthasen nur geringe Sequenzhomologie aufweist. Durch kinetische Untersuchungen der mutierten Enzyme konnte ein tieferer Einblick in den Reaktionsmechanismus archaealer Riboflavinsynthasen gewonnen werden.Lumazine synthases and riboflavin synthases are enzymes involved in riboflavin biosynthesis in many plants and microorganisms. The essence of this thesis was the biochemical characterization of these enzymes from several organisms and in part pathogens. In this work it was possible to get information about the structures and the reaction mechanisms of lumazine synthases and riboflavin synthases. Centre of this work was the site-directed mutagenesis with modification of amino acids at the active site on an archaeal riboflavin synthase with little sequence similarity to riboflavin synthases from eubacteria and plants. Kinetic analysis of the mutant enzymes gave more information about the reaction mechanism in archaeal riboflavin synthases
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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