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Biochemical characterization of an intermediate membrane subfraction in cyanobacteria involved in an assembly network for photosystem II
Get PDFOxygenic photosynthesis converts light energy into chemical energy and is responsible for generating most of our atmosphere’s oxygen and biomass on earth. Several multimeric protein complexes are involved in the underlying photosynthetic electron transfer chain with photosystem II (PSII) representing the initial complex mediating the extraction of electrons from water molecules, thus generating molecular oxygen as a by-product. During recent years, the structural details and components of the PSII complex, including its inorganic and organic cofactors, have been elucidated in great detail. However, little is known about the assembly pathway of this at least 20 protein subunits containing machinery. Previous work indicated that PSII assembly occurs in a step-wise fashion and requires a number of facilitating factors, which interact transiently with nascent PSII complexes. Earlier studies of one of those assembly factors, the cyanobacterial PratA protein, suggested that PSII biogenesis does not only underlie a temporal order but is also organized at the spatial level, as PratA was shown to mark a special intermediate membrane subfraction (PDMs), hypothesized to represent regions for initial steps of PSII biogenesis.
The presented work focused on a more detailed characterization of PDMs, clearly supporting their significance not only with regard to early protein assembly, but also concerning pigment synthesis and integration into the PSII precomplexes. The PDMs could further be allocated to special membrane regions, named biogenesis centers, at sites where thylakoid membranes converge to the plasma membrane, thus demonstrating the spatial organization of PSII assembly at the cellular level. Moreover, a novel function of PratA in preloading of PSII with Mn2+ ions, necessary for construction of the water-splitting complex, was discovered. Concomitantly with progression of the assembly, the nascent PSII complexes are transported from the PDMs to the thylakoid membrane system, where Sll0933 – a novel PSII assembly factor identified in this thesis – mediates the integration of the PSII inner antenna proteins followed by completion of the assembly process. Additionally, it could be shown that many of the so far identified facilitating factors interact with each other and, thus, form a complex network for PSII assembly. Especially the interaction between the two assembly factors YCF48 and Sll0933 was characterized in more detail, revealing a successive mode of action with YCF48 operating upstream of Sll0933. Taken together, the presented results enable the development of an extended and elaborated model of PSII assembly, which is a concerted process connecting protein and cofactor synthesis/integration in a spatiotemporal manner, and thus contribute to a more profound understanding of photosynthesis itself.Oxygene Photosynthese ermöglicht die Umwandlung von Lichtenergie in chemische Energie. Aufgrund des bei den zugrunde liegenden Reaktionen gebildeten molekularen Sauerstoffs (O2) stellt sie die Basis für den in unserer Atmosphäre angesammelten Sauerstoff und somit die Grundlage für höheres Leben auf der Erde dar. Die Entstehung von O2 wird von Photosystem II (PSII) katalysiert, dem ersten Komplex in einer Reihe von aus verschiedenen Bestandteilen aufgebauten Proteinkomplexen, welche den Transport von Elektronen zur Energiegewinnung vermitteln. Während die Zusammensetzung von PSII aus mindestens 20 verschiedenen Protein-Untereinheiten und diversen Co-Faktoren in den letzten Jahren weitgehend aufgeklärt wurde, ist das Wissen über den zugrunde liegenden Assemblierungsweg verhältnismäßig beschränkt. Bislang konnte gezeigt werden, dass dieser Ablauf schrittweise erfolgt und eine Reihe von Assemblierungsfaktoren erfordert. Dass die Biogenese von PSII neben ihrer zeitlichen Abfolge auch auf räumlicher Ebene organisiert ist, lässt sich aus früheren Studien eines dieser Assemblierungsfaktoren, des cyanobakteriellen PratA-Proteins schließen, welches eine spezielle Membranfraktion (PDMs) kennzeichnet, die offenbar an den frühen Schritten der PSII-Biogenese beteiligt ist.
Die hier gezeigten Ergebnisse einer detaillierteren Charakterisierung der PDMs unterstreichen ihre Bedeutung nicht nur im Hinblick auf die frühen Schritte der Assemblierung der Proteinuntereinheiten, sondern auch auf die Pigmentsynthese und deren Integration in PSII-Präkomplexe. Strukturell konnten PDMs sogenannten Biogenesezentren zugeordnet werden, welche sich an Stellen, an denen sich die Thylakoidmembranen der Plasmamembran annähern, befinden. Somit wurde die Frage der subzellulären Lokalisierung der PSII-Assemblierung beantwortet. Außerdem konnte eine Beteiligung von PratA an der Beladung von PSII mit Mn2+-Ionen zum Aufbau des Wasserspaltungsapparates gezeigt werden. Weitere Daten weisen darauf hin, dass mit zunehmender Assemblierung ein Transport der entstehenden PSII-Komplexe von den PDMs in Richtung der Thylakoidmembranen erfolgt. Unmittelbar nach Erreichen der Thylakoide scheint dann Sll0933 – ein neuer, in dieser Arbeit identifizierter PSII-Assemblierungsfaktor – die Integration der inneren PSII-Antennenproteine zu vermitteln. Der Abschluss der Assemblierung von PSII erfolgt ebenfalls im Thylakoidmembransystem. Es wurden außerdem Hinweise dafür erhalten, dass sich viele der bisher identifizierten Assemblierungsfaktoren gegenseitig beeinflussen und somit ein komplexes Netzwerk bilden. Insbesondere die Interaktion zwischen den beiden Assemblierungsfaktoren YCF48 und Sll0933 wurde detaillierter untersucht und führte zur Schlussfolgerung, dass YCF48 an früheren Schritten als Sll0933 an der PSII-Assemblierung beteiligt ist. Alles in allem handelt es sich bei der Assemblierung von PSII also um einen Prozess mit einer auf räumlicher und zeitlicher Ebene organisierten Verknüpfung von Integration der Protein-Untereinheiten und Synthese/Insertion der Co-Faktoren. Die dargestellten Ergebnisse ermöglichen eine deutliche Ausweitung des bisher geltenden Modells der PSII-Assemblierung und tragen somit zu einem besseren Gesamtverständnis des Prozesses der oxygenen Photosynthese an sich bei
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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