1,720,962 research outputs found
Mechanistic Insight into the Catechol Oxidase Activity by a Biomimetic Dinuclear Copper Complex
Full text linkThe biomimetic catalytic oxidation of 3,5-ditert-
butylcatechol by the dicopper(II) complex of the
ligand a,a¢-bis{bis[1-(1¢-methyl-2¢-benzimidazolyl)
methyl]amino}-m-xylene in the presence of dioxygen has
been investigated as a function of temperature and pH in
a mixed aqueous/organic solvent. The catalytic cycle
occurs in two steps, the first step being faster than the
second step. In the first step, one molecule of catechol is
oxidized by the dicopper(II) complex, and the copper(II)
centers are reduced. From the pH dependence, it is deduced
that the active species of the process is the
monohydroxo form of the dinuclear complex. In the
second step, the second molecule of catechol is oxidized
by the dicopper(I)-dioxygen complex formed upon
oxygenation of the reduced complex. In both cases,
catechol oxidation is an inner-sphere electron transfer
process involving binding of the catechol to the active
species. The binary catechol-dicopper(II) complex
formed in the first step could be characterized at very
low temperature (90 C), where substrate oxidation is
blocked. On the contrary, the ternary complex of dicopper(
I)-O2-catechol relevant to the second step does
not accumulate in solution and could not be characterized,
even at low temperature. The investigation of the
biphasic kinetics of the catalytic reaction over a range of
temperatures allowed the thermodynamic (DH and DS)
and activation parameters (DH „ and DS „ ) connected
with the key steps of the catecholase process to be
obtained
Tyrosinase-generated quinones induce covalent modification, unfolding, and aggregation of human holo-myoglobin.
No full textThe present study describes the pattern of protein modification undergone by human holo-myoglobin by reactive
fluoroquinones enzymatically produced by oxidation of 3-fluorophenol in mild conditions (pH 7.4, 25 °C). The
fluoroquinones react with a number of histidine residues. Surface residues H24, H36, H48, and H82 and the
heme distal histidine H64 were all found to be modified to a significant extent. In contrast, cysteine C110 is not
appreciably affected, possibly because it is not accessible to the fluoroquinones. The sites of protein modification
were assessed by mass spectrometry analysis of the peptide fragments resulting from controlled proteolysis of the
apoprotein. As a consequence of the reaction with quinones, the globular structure of myoglobin becomes more
prone to denaturation by the partial loss of its secondary structure. As a more intriguing consequence, the
fluoroquinones promote the formation of structured aggregates of moderate size that lack the typical morphology
of fibrillar structures
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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