1,720,979 research outputs found
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
Protein kinase CK2 mutants defective in substrate recognition - Purification and kinetic analysis
No full textFive mutants of protein kinase CK2 alpha subunit in which altogether 14 basic residues were singly to quadruply replaced by alanines (K74A,K75A,K76A,K77A; K79A, R80A,K83A; R191A,R195A,K198A; R228A; and R278A, K279A,R280A) have been purified to near homogeneity either as such or after addition of the recombinant beta subunit. By this latter procedure five mutated tetrameric holoenzymes were obtained as judged from their subunit composition, sedimentation coefficient on sucrose gradient ultracentrifugation, and increased activity toward a specific peptide substrate as compared with the isolated alpha subunits. The kinetic constants and the phosphorylation efficiencies (V(max)/Km) of all the mutants with the parent peptide RRRADDSDDDDD and a series of derivatives, in which individual aspartic acids were replaced by alanines, have been determined. Three mutants, namely K74A,K75A,K76A,K77A; K79A, R80A,K83A; and R191A,R195A, K198A, display dramatically lower phosphorylation efficiency and 8-50-fold higher Km values with the parent peptide, symptomatic of reduced attitude to bind the peptide substrate as compared with CK2 wild type. Such differences either disappear or are attentuated if the mutants R191A,R195A, K198A; K79A,R80A,K83A; and K74A,K75A, K76A,K77A are assayed with the peptides RRRADDSADDDD, RRRADDSDDADD, and RRRADDSDDDAA, respectively. In contrast, the phosphorylation efficiencies of the other substituted peptides decrease more markedly with these mutants than with CK2 wild type. These data show that one or more of the basic residues clustered in the 191-198, 79-83, and 74-77 sequences are implicated in the recognition of the acidic determinants at positions +1, +3, and +4/+5, respectively, and that if these residues are mutated, the relevance of the other acidic residues surrounding serine is increased. In contrast the other two mutants, namely R228A and R278A,K279A, R280A, display with all the peptides V(max) values higher than CK2 wild type, counterbalanced however by somewhat higher Km values. It can be concluded from these data that all five mutations performed are compatible with the reconstitution of tetrameric holoenzyme, but all of them influence the enzymatic efficiency of CK2 to different extents. Although the basic residues mutated in the 74-77, 79-83, and 191-198 sequences are clearly implicated in substrate recognition by interacting with acidic determinants at variable positions downstream from serine, the other basic residues seem to play a more elusive and/or indirect role in catalysis
A multifunctional network of basic residues confers unique propertiers to protein kinase CK2
No full textProtein kinase CK2 is characterized by a number of features, including substrate specificity, inhibition by polyanionic compounds and intrasteric down-regulation by its beta-subunit, which denote a special aptitude to interact with negatively charged ligands. This situation may reflect the presence in CK2 catalytic subunits of several basic residues that are not conserved in the majority of other protein kinases. Some of these residues, notably K49 in the 'Gly rich loop', K74, K75, K76, K77, K79, R80, K83 in the 'Lys rich segment' and R191, R195, K198 in the 'p+1 loop', have been shown by mutational studies to be implicated to various extents and with distinct roles in substrate recognition, inhibition by heparin and by pseudosubstrate and instrasteric regulation. Molecular modelization based on crystallographic data provide a rationale for the biochemical observations, showing that several of these basic residues are clustered around the active site where they make contact with individual acidic residues of the peptide substrate. They can also mediate the effect of polyanionic inhibitors (e.g. heparin) and of regulatory elements present in the beta-subunit, in the N terminal segment of the catalytic subunit and possibly in other proteins interacting with CK2. Our data also disclose a unique mode of binding of the phosphoacceptor substrate which bridges across the catalytic cleft making contacts with both the lower and upper lobes of CK2
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
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