1,720,959 research outputs found
Duplication of the mmoX gene in Methylosinus sporium: cloning, sequencing and mutational analysis
No full textThe soluble methane monooxygenase (sMMO) is a key enzyme for methane oxidation, and is found in only some methanotrophs, including Methylosinus sporium 5. sMMO expression is regulated at the level of transcription from a ? 54 promoter by a copper-switch, and is only expressed when the copper-to-biomass ratio during growth is low. Extensive phylogenetic and genetic analyses of sMMOs and other soluble di-iron monooxygenases reveal that these enzymes have only been acquired relatively recently through horizontal gene transfer. In this study, further evidence of horizontal gene transfer was obtained, through cloning and sequencing of the genes encoding the sMMO enzyme complex plus the regulatory genes mmoG and mmoR, and identification of a duplicate copy of the mmoX gene in Ms. sporium. mmoX encodes the ? subunit of the hydroxylase of the sMMO enzyme, which constitutes the active site ( Prior & Dalton, 1985 ). The mmoX genes were characterized at the molecular and biochemical levels. Although both copies were transcribed, only mmoX copy 1 was essential for sMMO activity. Construction of an sMMO? mutant by marker-exchange mutagenesis gave some possible insights into the role of the water-soluble pigment in siderophore-mediated iron acquisition. Finally, the amenability of Ms. sporium to genetic manipulation was demonstrated by complementing the sMMO? mutant by heterologous expression of sMMO genes from Methylosinus trichosporium OB3b and Methylococcus capsulatus (Bath), and it was shown that Ms. sporium could be used as an alternative model organism for molecular analysis of MMO regulatio
Involvement of MmoR and MmoG in the transcriptional activation of soluble methane monooxygenase genes in Methylosinus trichosporium OB3b
No full textMethanotrophs oxidize methane to methanol using the enzyme methane monooxygenase. Methylosinus trichosporium OB3b has two such enzymes: a membrane-bound particulate methane monooxygenase (pMMO) and a soluble, cytoplasmic methane monooxygenase (sMMO). In methanotrophs possessing both enzymes, the expression of the genes encoding sMMO and pMMO is regulated by copper ions, with sMMO expressed solely when copper is limiting. Virtually nothing is known about the specific machinery involved in the copper-regulated transcription of mmo genes except the identification of two proteins necessary for the expression: a Sigma 54-dependent transcriptional activator, MmoR, and a putative GroEL-like chaperone, MmoG. Genes encoding mmoR and mmoG are located immediately upstream of those encoding sMMO in the genome of M. trichosporium OB3b. Here, we use a green fluorescent protein promoter probe vector to show that nearly the complete intergenic DNA sequence between mmoG and mmoX is absolutely required for transcriptional activation. Furthermore, we used gel-shift assays to demonstrate that both MmoR and MmoG were required for protein binding to this region of DNA
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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