1,720,957 research outputs found
Minimal actin cortices: The αD-helix of ezrin's C-ERMAD governs F-actin binding
No full texthttp://dx.doi.org/10.13039/501100001659 German Research Foundationhttp://dx.doi.org/10.13039/501100002347 BMBF Bon
Influence of ezrin's actin binding properties on the formation of minimal actin cortices
Full text linkThe cytoskeleton is a pivotal structure within cells, crucial for their motion and life-indispensable processes. The actin cortex is a dense actin network that is part of the cytoskeleton and linked to the plasmamembrane. ERM (ezrin, radixin and moesin) proteins are central for the connection between the actin cortex and plasmamembrane. Ezrin recruits filamentous actin (f-actin) to the plasmamembrane resulting in the formation of actin cortex structures. In vivo, ezrin is activated in a two step mechanism. First, ezrin binds with its N-terminal domain (ezrin-FERM) to L-α -phosphatidylinositol-4,5-bisphosphate (PtdIns(4,5)P2) at the plasmamembrane. This induces a conformational change, that allows the C-terminal domain of ezrin to bind f-actin. A phosphorylation of threonine at position 567 stabilises the open conformation of ezrin and makes it fully active. In vitro a phosphomimetic mutation is inserted to circumvent the phosphorylation (ezrin T567D).
In this project, mutations were inserted into the actin binding site of ezrin T567D, to alter its actin binding properties. The mutations R569A, I580A, I571M and K577A were selected and compared to the unmodified actin binding site of ezrin T567D. The mutations were selected on a literature review and displayed different co-sedimentation ratios with f-actin. Since ezrin is activated by binding to PtdIns(4,5)P2, it was verified that the binding affinity of this interaction was not changed upon the inserted mutations.
The ezrin-actin binding strength was measured by means of atomic force microscopy measurements with the colloidal probe technique (CPT). Force-distance curves between the with the ezrin mutants funtionalised colloidal probe and an f-actin layer were recorded and the ezrin-actin binding properties were determined. The mutation R569A and I580A resulted in a stronger actin binding compared to ezrin T567D, whereas I571M and K577A decreased the binding strength.
Minimal actin cortices (MACs) formed by the ezrin mutants were investigated by means of fluorescence microscopy. Hereby the architecture and dynamics of the bound f-actin were analysed. The mutation I571M and K577A were not able to form stable MACs and could only bind f-actin transiently. Ezrin with the additional R569A or I580A mutation was able to attach more f-actin to the surface with less PtdIns(4,5)P2 in the membrane compared to ezrin T567D. The adhesion strength revealed a limit, at which ezrin is not able to bind f-actin steadily. The ezrin T567D passes this limit within the observed PtdIns(4,5)P2 content regime that is comparable to physiological PtdIns(4,5)P2 concentration.
These results demonstrate the importance of ezrin's weak actin binding strength, that enables the control of f-actin recruitment via increased PtdIns(4,5)P2 concentrations within the membrane.2024-11-1
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
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