1,720,959 research outputs found
Re-using Biological Devices: Characterization and Mathematical Modeling of Protein- and CRISPRi-mediated Regulation Devices to Design Predictable Interconnected Circuits with Reduced Cell Load
No full textProbing RNA catalysis in protocellular settings relevant to the origin of life
Full text linkThe emergence of life has long been a topic of high interest. Of the many hypotheses pro-posed for the emergence of early cellular predecessors of our last universal common ances-tor (LUCA), the RNA World hypothesis is a prime candidate. It posits a time before the evolution of modern DNA / protein-based life, where both roles of information storage and processing were played by RNA, while DNA and complex proteins had not yet evolved. With the advent of in vitro evolution, selection experiments have yielded a variety of dif-ferent catalytic RNAs (ribozymes) able to catalyse a range of chemical reactions in a se-quence-dependent manner. Nonetheless, a number of outstanding problems remain, such as the dissemination of genetic information among protocell populations in the absence of complex cell division machinery, genotype-phenotype coupling in RNA-peptide based membrane-less compartments and finally, the general sequence-independent templating abilities of ribozymes. In this work, cycles of freezing and thawing were employed to drive the proliferation of encapsulated RNA replicators among feedstock vesicles, allowing their survival following multiple rounds of dilution via self-amplification, thereby enabling a primitive form of lateral gene transfer among protocell populations and eliminating the need for sophisticated cell division apparatus. In the following section, a ribozyme ligase was re-engineered to perform concatenated ligation of an RNA substrate leading to a drastic increase in length. Ribozyme activity was subsequently characterised in the presence of short lysine homopeptides that allow phase separation and RNA partitioning. Moreover, ribozyme activity was found to modulate the physical properties of coacervates, demon-strating a primitive form of genotype-phenotype linkage in membraneless model protocells. Finally, a group I intron-derived ribozyme ligase that performs templated ligation reaction was employed as a general templated RNA ligase and characterised for the synthesis of a variety of functional RNA sequences. The system was subsequently adopted by collabora-tors as a starting point for the development of environmentally-driven RNA replication systems. Taken together, the data presented here offer insight into the possible mechanisms for persistence and proliferation of prebiotically relevant protocell models in environmental settings as well as an overview of the ‘proto-biosphere’ on early Earth and potential transi-tional stages of chemical and biological evolution leading to the emergence of the first cellular systems as we know them.Die Entstehung des Lebens ist seit langem ein Thema von großem Interesse. Von den vielen Hypothesen, die für die Entstehung früher zellulärer Vorläufer unseres letzten gemeinsamen Vorfahren vorgeschlagen wurden, ist die RNA-Welt-Hypothese ein Hauptkandidat. Sie geht von einer Zeit vor der Evolution des modernen DNA-/Protein-basierten Lebens aus, in der die RNA sowohl die Rolle der Informationsspeicherung als auch die der Informationsverarbeitung übernahm, während sich die DNA und komplexe Proteine noch nicht entwickelt hatten. Mit dem Aufkommen der In-vitro-Evolution haben Selektionsexperimente eine Vielzahl verschiedener katalytischer RNAs (Ribozyme) hervorgebracht, die in der Lage sind, eine Reihe chemischer Reaktionen in sequenzabhängiger Weise zu katalysieren. Dennoch gibt es noch eine Reihe offener Probleme, wie z. B. die Verbreitung genetischer Informationen zwischen den Populationen von Protozellen in Abwesenheit einer komplexen Zellteilungsmaschinerie, die Genotyp-Phänotyp-Kopplung in membranlosen Kompartimenten auf RNA-Peptidbasis und schließlich die allgemeinen sequenzunabhängigen Template-Fähigkeiten von Ribozymen. In dieser Arbeit wurden Zyklen des Einfrierens und Auftauens eingesetzt, um die Vermehrung eingekapselter RNA-Replikatoren in den Ausgangsvesikeln anzutreiben und ihr Überleben nach mehreren Verdünnungsrunden durch Selbstamplifikation zu ermöglichen, wodurch eine primitive Form des lateralen Gentransfers zwischen Protozellpopulationen ermöglicht wird und die Notwendigkeit eines hochentwickelten Zellteilungsapparats entfällt. Im folgenden Abschnitt wurde eine Ribozym-Ligase so umgestaltet, dass sie eine verkettete Ligation eines RNA-Substrats durchführt, was zu einer drastischen Zunahme der Länge führt. Die Ribozymaktivität wurde anschließend in Gegenwart von kurzen Polylysin-Polymeren charakterisiert, die eine Phasentrennung und RNA-Verteilung ermöglichen. Darüber hinaus wurde festgestellt, dass die Ribozymaktivität die physikalischen Eigenschaften von Koazervaten moduliert, was eine primitive Form der Genotyp-Phänotyp-Verknüpfung in membranlosen Modell-Protozellen demonstriert. Schließlich wurde eine von einem Gruppe-I-Intron abgeleitete Ribozym-Ligase, die eine matrizenabhängige Ligationsreaktion durchführt, als allgemeine RNA-Ligase eingesetzt und für die Synthese verschiedener funktioneller RNA-Sequenzen charakterisiert. Das System wurde anschließend von Kollaborationspartnern als Ausgangspunkt für die Entwicklung von umweltgesteuerten RNA-Replikationssystemen übernommen. Zusammengenommen bieten die hier vorgestellten Daten einen Einblick in mögliche Persistenz- und Vermehrungsstrategien präbiotisch relevanter Protozellmodellen sowie einen Überblick über eine mögliche "Proto-Biosphäre" auf der frühen Erde und potentielle evolutionäre Zwischenstufen, die zur Entstehung der ersten zellulären Systeme geführt haben könnten
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
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
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