1,720,956 research outputs found
Structural and functional characterization of redox metabolism and carbon partitioning enzymes in Euglena gracilis. Study of the importance in regulating the synthesis and degradation of paramylon
No full textFil: Calloni, Rodrigo Daniel. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas; Argentina.Euglena gracilis es un protista unicelular fotosintético que ha llamado la atención por su resistencia al estrés causado por metales pesados y por sintetizar metabolitos de interés comercial, entre ellos el paramilón. Este es su polímero de reserva, un beta-1,3-glucano insoluble en agua. La información enzimológica referente al metabolismo redox y del paramilón en E. gracilis aún es limitada. Por esta razón, seleccionamos las enzimas glutamato cisteína ligasa (EgrGCL, EC 6.3.2.2), glicosil fosforilasa de la familia 149 (EgrGH149, EC 2.4.1) y glicosil hidrolasa de la familia 64 (EgrGH64, EC 3.2.1.39) para realizar la producción recombinante y estudiarlas desde distintos enfoques.
EgrGCL presenta actividad empleando como sustratos ATP, cisteína y glutámico con parámetros cinéticos similares a lo observado en otras GCL caracterizadas.
EgrGH149 es específica para la utilización de beta-1,3-glucanos de baja masa molecular como sustrato, sin evidenciar actividad con beta-1,3-glucanos de alta masa molecular. Identificamos residuos relevantes en la catálisis por primera vez en una enzima de esta familia. EgrGH149 se encontraría contigua a los gránulos de paramilón formando agrupaciones.
Esta es la primera vez que una beta-1,3-endoglucanasa de E. gracilis es producida recombinantemente usando un sistema de expresión procariota. EgrGH64 evidenció actividad enzimática empleando los sustratos laminarina, paramilón y beta-glucano de pared celular de levadura. El principal producto de hidrólisis de EgrGH64 fue laminaripentaosa. Evidenciamos la presencia de esta enzima en determinadas condiciones de cultivo y su efecto antifúngico.
Los conocimientos generados en este trabajo de Tesis nos aportan una mejor comprensión del contexto metabólico de E. gracilisEuglena gracilis is a photosynthetic unicellular protist. It has attracted attention for its resistance to heavy metal stress and the synthesis of commercially interesting metabolites. Paramylon is its storage polymer, a water-insoluble beta-1,3-glucan. There is a lack of information regarding redox and paramylon metabolism. The enzymes glutamate cysteine ligase (EgrGCL, EC 6.3.2.2), glycosyl phosphorylase family 149 (EgrGH149, EC 2.4.1) and glycosyl hydrolase family 64 (EgrGH64, EC 3.2.1.39) where select to perform recombinant production and study them from different approaches.
We observed activity in EgrGCL using ATP, cysteine and glutamic acid as substrates. The kinetic parameters were like those observed in other characterized GCLs.
EgrGH149 is specific for the use of low molecular weight beta-1,3-glucans as substrates, without activity with high molecular weight beta-1,3-glucans. For the first time in an enzyme of this family, we identified residues relevant in catalysis. EgrGH149 would be found forming clusters adjacent to the paramylon granules.
This is the first time that a beta-1,3-endoglucanase from E. gracilis has been produced in a recombinant form using a prokaryotic expression system. EgrGH64 showed enzymatic activity using laminarin, paramylon and yeast cell wall β-glucan as substrates. The main hydrolysis product of EgrGH64 was laminaripentaose. We observed the antifungal effect of this enzyme under certain culture conditions. The knowledge generated in this work provides a better understanding of E. gracilis metabolic context.Consejo Nacional de Investigaciones Científicas y TécnicasAgencia Nacional de Promoción Científica y TecnológicaUniversidad Nacional del Litora
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
Elucidating carbohydrate metabolism in Euglena gracilis: Reverse genetics-based evaluation of genes coding for enzymes linked to paramylon accumulation
No full textEuglena gracilis is a eukaryotic single-celled and photosynthetic organism grouped under the kingdom Protista. This phytoflagellate can accumulate the carbon photoassimilate as a linear β-1,3-glucan chain called paramylon. This storage polysaccharide can undergo degradation to provide glucose units to obtain ATP and reducing power both in aerobic and anaerobic growth conditions. Our group has recently characterized an essential enzyme for accumulating the polysaccharide, the UDP-glucose pyrophosphorylase (Biochimie vol 154, 2018, 176–186), which catalyzes the synthesis of UDP-glucose (the substrate for paramylon synthase). Additionally, the identification of nucleotide sequences coding for putative UDP-sugar pyrophosphorylases suggests the occurrence of an alternative source of UDP-glucose. In this study, we demonstrate the active involvement of both pyrophosphorylases in paramylon accumulation. Using techniques of single and combined knockdown of transcripts coding for these proteins, we evidenced a substantial decrease in the polysaccharide synthesis from 39 ± 7 μg/106 cells determined in the control at day 21st of growth. Thus, the paramylon accumulation in Euglena gracilis cells decreased by 60% and 30% after a single knockdown of the expression of genes coding for UDP-glucose pyrophosphorylase and UDP-sugar pyrophosphorylase, respectively. Besides, the combined knockdown of both genes resulted in a ca. 65% reduction in the level of the storage polysaccharide. Our findings indicate the existence of a physiological dependence between paramylon accumulation and the partitioning of sugar nucleotides into other metabolic routes, including the Leloir pathway's functionality in Euglena gracilis.Fil: Muchut, Robertino José. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Agrobiotecnología del Litoral. Universidad Nacional del Litoral. Instituto de Agrobiotecnología del Litoral; ArgentinaFil: Calloni, Rodrigo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Agrobiotecnología del Litoral. Universidad Nacional del Litoral. Instituto de Agrobiotecnología del Litoral; ArgentinaFil: Arias, Diego Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Agrobiotecnología del Litoral. Universidad Nacional del Litoral. Instituto de Agrobiotecnología del Litoral; ArgentinaFil: Arce, Agustín Lucas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Agrobiotecnología del Litoral. Universidad Nacional del Litoral. Instituto de Agrobiotecnología del Litoral; ArgentinaFil: Iglesias, Alberto Alvaro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Agrobiotecnología del Litoral. Universidad Nacional del Litoral. Instituto de Agrobiotecnología del Litoral; ArgentinaFil: Guerrero, Sergio Adrian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Agrobiotecnología del Litoral. Universidad Nacional del Litoral. Instituto de Agrobiotecnología del Litoral; Argentin
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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