1,720,976 research outputs found
Probing the substrate specificity for lipases. II. Kinetic and Modeling Studies on the Molecular Recognition of 2-Arylpropionic Esters by Candida rugosa and Rhizomucor miehei Lipases
No full textRacemic arylpropionic esters 1-3, precursors of therapeutically important non-steroidal antiinflammatory drugs, were subjected to hydrolyses in the presence of either Candida rugosa or Rhizomucor miehei crude lipases. The hydrolyses of 1 and 2 proved to be highly enantioselective, whereas 3 was not transformed at all. Both the substrate specificity and the enantioselectivity of these lipases were explained through a molecular modeling study involving docking experiments between 1-3 and the amino acids forming the enzymes active-sites, whose three-dimensional structures were obtained from X-ray crystallographic data, followed by extensive conformational analysis on their computer-generated complexes. The results of this study also account for the high enantioselective and good yielding hydrolysis of 3 (as the corresponding 2-chloroethyl ester) catalyzed by CRL pretreated with 2-propanol, recently reported in the literature, and lead to admit that such a treatment may operate very deep conformational changes on the amino acids of the enzyme active-site
Probing the substrate specificity for lipases. A CoMFA approach for predicting the hydrolysis rates of 2-arylpropionic esters catalyzed by Candida rugosa lipase
No full textThe enzyme catalyzed hydrolysis of esters 1-3, precursors of therapeutically important non-steroidal antiinflammatory drugs, in the presence of the lipase from Candida rugosa was studied and the relative rates of the enzymatic hydrolysis were determined. With the exception of 3, which was not transformed under the reaction conditions, all transformations proved to be highly enantiospecific. Usually the mechanism of enantiorecognition is probed by substrate mapping. Although more theoretical approaches are existing, these all require knowledge of the three-dimensional structure of the enzyme. A model capable of correlating the extent of substrate hydrolysis as well as the initial reaction rates with their stereoelectronic properties has been developed by a Comparative Molecular Field Analysis (CoMFA) approach. This model does not require detailed knowledge of the three-dimensional structure of the enzyme and proved to be highly predictive. It is possible that this kind of approach holds promise for future work on enzyme-substrate interactions
A new class of Polyvinyl alcohol polymers as stationary phases to separate Candida rugosa lipase isoforms by hydrophobic chromatography.
No full textA three step chromatographic procedure and electrophoretic characterization of an active isoform of Candida rugosa Lipases.
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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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