1,720,968 research outputs found
Antioxidant system of peroxiredoxins in Sulfolobus solfataricus.
No full textThe maintenance of the proper intracellular redox environment in aerobic microorganisms is guaranteed by redox systems and antioxidants that safeguard cells from the attack of reactive oxgen species (ROS) such as superoxide anions (O∙-), hydrogen peroxide (H2O2), hydroxyl radicals (OH∙). The increase of ROS concentration inside the cell damage biomolecules, membranes and essential metabolic functions. To kept low the intracellular level of ROS the cells are equipped of an array of antioxidant systems that have in the first line the superoxide dismutase (SODs) that catalyze the dismutation of O∙- to form H2O2 and oxygen. The H2O2 is reduced by different systems represented mainly by catalases and peroxidases.
The peroxiredoxins (Prx) are thiol-peroxidase that can scavange the peroxides utilizing generally Thioredoxin Reductase (TR) / Thioredoxin (Trx) system as electron donors that allow the recycling of the enzymes (1). Prxs are ubiquitous enzymes that share the same basic catalytic mechanisms, in which an activated cysteine (the peroxidative cysteine) is oxidized to sulphenic acid by peroxide substrate. Reductive regeneration of the oxidized catalytic thiol generally depends on glutathione, thioredoxin, glutaredoxin, cyclophilin and tryparedoxin.
The aim of this project is to expand the knowledge on antioxidant system in Sulfolobus solfataricus. For this purpose we have expressed in E. coli and characterized the four Prxs, Bcp1, Bcp2 (2), Bcp3, Bcp4. The purified recombinant proteins are able to remove both H2O2 and tert-butyl hydroperoxide and show high thermostability. Furthermore Bcp1, Bcp3 and Bcp4 can use as electron donor in the reycling of enzymes, the redox system Protein Disulfide Oxidoreductase (SsPDO) / TR previously characterized in S.solfataricus (3) while Bcp2 can use only DTT.
Comparative functional and transcriptional analysis suggest different role of Bcps during oxidative stress: Bcp2 and Bcp3 could act as inducible enzyme when the cell are attacked by exogenous peroxides, while Bcp1 and Bcp4 could support a protective role against endogenous peroxide formed during metabolism
Peroxiredoxins as cellular guardians in Sulfolobus solfataricus characterization of Bcp1, Bcp3 and Bcp4.
No full textPeroxiredoxins are ubiquitous enzymes that are part of the oxidative stress defense system. In the present study, we identified three peroxiredoxins [bacterioferritin comigratory protein (Bcp)1, Bcp3 and Bcp4] in the genome of the aerobic hyperthermophilic archaeon Sulfolobus solfataricus. Based on the cysteine residues conserved in the deduced aminoacidic sequence, Bcp1 and Bcp4 can be classified as 2-Cys peroxiredoxins and Bcp3 as a 1-Cys peroxiredoxin. A comparative study of the recombinant Bcps produced in Escherichia coli showed that these enzymes protect DNA plasmid from oxidative damage and remove both H2O2 and tert-butyl hydroperoxide, although at different efficiencies. We observed that all of them were particularly thermostable and that peak enzymatic activity fell within the range of the growth temperature of S. solfataricus. Furthermore, we discovered an alternative Bcp reduction system whose composition differs from that of the peroxiredoxin reduction system previously characterized in the aerobic hyperthermophilic archaeon Aeropyrum pernix. Whereas the latter uses the thioredoxin/thioredoxin reductase/NADPH system, this alternative Bcp system is formed of the protein disulfide oxidoreducatase, SSO0192, the thioredoxin reductase, SSO2416, and NADPH. The role of Bcps in oxidative stress was investigated using transcriptional analysis. Different northern blot analysis responses suggested that the Bcp antioxidant system of S. solfataricus can both operate at the constitutive level, with Bcp1 and Bcp4 preventing endogenous peroxide formation, and at the inducible level, with Bcp3 and the already characterized Bcp2 protecting cells from the attack of external peroxides
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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