1,720,977 research outputs found
Redox biochemistry of Pyrococcus furiosus: Fundamental and applied aspects
No full textIn Pyrococcus furiosus (Pfu) ferredoxin (Fd) replaces NAD+ for carrying reducing equivalent to the oxidative phosphorylation machinery, and it also takes part in the regeneration of NADPH, which is necessary for biosynthetic pathways. Therefore, it plays a central role in various metabolic pathways of the organism. PfuFd is one of the most extensively studied ferredoxins, however, some fundamental aspects remain elusive. This thesis work focuses on some of the unresolved features of the protein. Initially PfuFd was isolated as a dimer of 12-13 kDa, however, all the subsequent studies described the protein as a monomer without any experimental evidence. All (putative) natural electron-transfer partners of PfuFd are redox enzymes catalyzing two-electron reactions while ferredoxin is a one-electron carrier. It is possible that ferredoxin may interact with the redox partner enzymes in the dimeric form. Therefore, it is important to resolve the dilemma regarding the oligomeric state of the protein (chapter 2). The intra-cellular ionic strength of P. furiosus was determined to be ca. 350 mM, at which ferredoxin occurs predominantly in the dimeric form. Transition from the dimeric to monomeric form is observed at a salt concentration higher than 350 mM. We hypothesize that ferrdoxin is a dimer in vivo. PfuFd demonstrates conservation of the minimal domain containing the cluster coordinating consensus sequence. However, the cluster is coordinated by three cysteines and one aspartate residue instead of by four cysteines. In addition, two additional cysteines are present which raises the possibility of a disulfide bond formation between them. In some earlier studies the formation of a disulfide bond was demonstrated under aerobic condition and a possible contribution of the disulfide bond to the redox chemistry of the protein has been described. However, formation of a disulfide bond under the strongly reducing intracellular condition of an anaerobic organism like P. furiosus is not understandable. We demonstrate (in chapter 3) that these additional cysteines do not form a disulfide bond under intra-cellular mimicking conditions. Observing the effects of site directed mutagenesis, we attribute to the free cysteines an important structural role in the hyperthermostability of the protein. Ferredoxin, cytochrome c, rubredoxin, etc. are small electron-transfer protein and they possess well characterised metal cofactors. Electrochemistry has been successfully applied in studying the intricate properties of these electron-transfer proteins mainly in solution. However, solution voltammetry suffers from various problems like mass transport / diffusion limitation, requirement of promoters, which can be avoided by immobilizing the protein on the electrode surface. A stable and functional PfuFd immobilized gold electrode has been developed, which shows a similar electrochemical response as in the solution voltammetry. The transition between the dimeric and monomeric state on the electrode is observed in an atomic force microscopic (AFM) setup. X-ray photoelectron spectrocopy (XPS) confirms the formation of gold-thiol bonds. We find the ferredoxin electrode to be a useful tool for studying the catalytic mechanisms of the associated redox enzymes from P. furiosus. We have thus studied two redox enzymes, glyceraldehyde-3-phosphate oxidoreductase (GAPOR) and aldehyde oxidoreductase (AOR), which are involved in ferredoxin-mediated redox processes in the organism. Addition of these enzymes at room temperature results in complex formation between the electrode-bound ferredoxin and the enzyme. At 60 °C a catalytic wave appears upon addition of the substrate, glyceraldehyde-3-phosphate to the Fd-GAPOR complex. In the case of AOR at 80 °C reversible oxidation of crotonadehyde to crotonic acid and vice versa was observed. This work opens the way for the application of Fd electrodes in achieving controlled reduction of carboxylic acids on a preparative scale.Applied Science
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Variations on the Author
Get PDF“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
Get PDFWe 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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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