1,720,995 research outputs found
Crystal structure of a methyltransferase from a no-known-vector Flavivirus
No full textPresently known flaviviruses belong to three major evolutionary branches: tick-borne viruses, mosquitoborne viruses and viruses with no known vector. Here we present the crystal structure of the Yokose virus methyltransferase at 1.7 angstrom resolution, the first structure of a methyltransferase of a Flavivirus with no known vector. Structural comparison of three methyltransferases representative of each of the Flavivirus branches shows that fold and structures are closely conserved, most differences being related to surface loops flexibility. Analysis of the conserved residues throughout all the sequenced flaviviral methyltransferases reveals that, besides the central cleft hosting the substrate and cofactor binding sites, a second, almost continuous, patch is conserved and points away from active site towards the back of the protein. The high level of structural conservation in this region could be functional for the methyl transferase/RNA interaction and stabilization of the ensuing complex
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
Flaviviral methyltransferase/RNA interaction: structural basis for enzyme inhibition
No full textFlaviviruses are the causative agents of severe diseases such as Dengue or Yellow fever. The replicative machinery used by the virus is based on few enzymes including a methyltransferase, located in the N-terminal domain of the NS5 protein. Flaviviral methyltransferases are involved in the last two steps of the mRNA capping process, transferring a methyl group from S-adenosyl-L-methionine onto the N7 position of the cap guanine (guanine-N7 methyltransferase) and the ribose 2'O position of the first nucleotide following the cap guanine (nucleoside-2'O methyltransferase). The RNA capping process is crucial for mRNA stability, protein synthesis and virus replication. Such an essential function makes methyltransferases attractive targets for the design of antiviral drugs. In this context, starting from the crystal structure of Wesselsbron flavivirus methyltransferase, we elaborated a mechanistic model describing protein/RNA interaction during N7 methyl transfer. Next we used an in silico docking procedure to identify commercially available compounds that would display high affinity for the methyltransferase active site. The best candidates selected were tested in vitro to assay their effective inhibition on 2'O and N7 methyltransferase activities on Wesselsbron and Dengue virus (Dv) methyltransferases. The results of such combined computational and experimental screening approach led to the identification of a high-potency inhibitor
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
De novo initiation of RNA synthesis by the arterivirus RNA-dependent RNA polymerase
No full textAll plus-strand RNA viruses encode an RNA-dependent RNA polymerase (RdRp) that functions as the catalytic subunit of the viral replication/transcription complex, directing viral RNA synthesis in concert with other viral proteins and, sometimes, host proteins. RNA synthesis essentially can be initiated by two different mechanisms, de novo initiation and primer-dependent initiation. Most viral RdRps have been identified solely on the basis of comparative sequence analysis, and for many viruses the mechanism of initiation is unknown. In this study, using the family prototype equine arteritis virus (EAV), we address the mechanism of initiation of RNA synthesis in arteriviruses. The RdRp domains of the members of the arterivirus family, which are part of replicase subunit nsp9, were compared to coronavirus RdRps that belong to the same order of Nidovirales, as well as to other RdRps with known initiation mechanisms and three-dimensional structures. We report here the first successful expression and purification of an arterivirus RdRp that is catalytically active in the absence of other viral or cellular proteins. The EAV nsp9/RdRp initiates RNA synthesis by a de novo mechanism on homopolymeric templates in a template-specific manner. In addition, the requirements for initiation of RNA synthesis from the 3′ end of the viral genome were studied in vivo using a reverse genetics approach. These studies suggest that the 3′-terminal nucleotides of the EAV genome play a critical role in viral RNA synthesis
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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