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Production of the persulfurated form of Azotobacter vinelandii RhdA : a rhodanese-like protein that could behave as sulfane sulfur delivery protein
No full textUNRAVELLING FUNCTIONAL INTERACTIONS OF THE RHODANESE-LIKE PROTEIN RhdA OF AZOTOBACTER VINELANDII
Full text linkThe subjects of the present investigation were A. vinelandii RhdA and E.coli SseA, that in the rhodanese-domain panorama represent two prototypes of tandem-domain rhodanese proteins. They belong to two different subfamilies: TSTs and MSTs and their active-site motifs, (CRXGX[R/T]) and (CG[S/T]GVT) respectively, are considered important in driving substrate recognition.
In this work, multiple approaches were exploited with the aim of elucidating physiological role(s) of RhdA. We first focused on searching a possible metabolic pathway involving RhdA. Starting from the experimental evidence of direct sulfane sulfur transfer from E. coli IscS to RhdA (Forlani et al., 2005), we analyzed whether RhdA could function as sulfane sulfur acceptor of A. vinelandii cysteine desulfurases taking in account the importance of the trafficking of the persulfide in the biosynthetic pathways (Meuller 2006).
Secondly, RhdA and SseA biological role(s) were investigated in vivo, taking advantage of the availability of an A. vinelandii mutant strain lacking rhdA gene (Colnaghi et al, 1996) and of an E. coli mutant strain lacking sseA gene (Celestini 2001). Different growth conditions in presence or in absence of oxidative agents have been evaluated, starting from the evidence that the RhdA null mutant MV474 was more prone than the wild-type strain UW136 to oxidative stress (Cereda et al., 2007)
Mobilization of sulfane sulfur from cysteine desulfurases to the Azotobacter vinelandii sulfurtransferase RhdA
Full text linkMobilization of the l-cysteine sulfur for the persulfuration of the rhodanese of Azotobacter vinelandii, RhdA, can be mediated by the A. vinelandii cysteine desulfurases, IscS and NifS. The amount of cysteine was higher in mutant strains lacking rhdA (MV474) than in wild type. The diazotrophic growth of MV474 was impaired. Taking into account the functional results about rhodanese-like proteins and RhdA itself, it is suggested that RhdA-dependent modulation of l-cysteine levels must deal with a redox-related process
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
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