1,720,986 research outputs found
Site-directed mutagenesis identifies active-site residues of the light chain of botulinum neurotoxin type A
No full textIF 2.93
Botulinum neurotoxins are metalloproteases specific for SNARE proteins involved in neuroexocytosis
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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
Bacterial toxins with intracellular protease activity
No full textThe recent determination of their primary sequence has lead to the discovery of the metallo-proteolytic activity of the bacterial toxins responsible for tetanus, botulism and anthrax. The protease domain of these toxins enters into the cytosol where it displays a zinc-dependent endopeptidase activity of remarkable specificity. Tetanus neurotoxin and botulinum neurotoxins type B, D, F and G cleave VAMP, an integral protein of the neurotransmitter containing synaptic vesicles. Botulinum neurotoxins type A and E cleave SNAP-25, while the type C neurotoxin cleaves both SNAP-25 and syntaxin, two proteins located on the cytosolic face of the presynaptic membrane. Such specific proteolysis leads to an impaired function of the neuroexocytosis machinery with blockade of neurotransmitter release and consequent paralysis. The lethal factor of Bacillus anthracis is specific for the MAPkinase-kinases which are cleaved within their amino terminus. In this case, however, such specific biochemical lesion could not be correlated with the pathogenesis of anthrax. The recently determined sequence of the vacuolating cytotoxin of Helicobacter pylori contains within its amino terminal domain elements related to serine-proteases, but such an activity as well as its cytosolic target remains to be detected
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
A lysolecithin/fatty acid mixture promotes and then blocks neurotransmitter release at the Drosophila melanogaster larval neuromuscular junction
No full textThe study of the effect of snake presynaptic neurotoxins with phospholipase A2 activity on nerve terminals has recently unveiled the inhibitory action of a lysophosphatidylcholine (LysoPC)/fatty acid mixture. We report here that these neurotoxins have no activity on Drosophila melanogaster nerve terminals. However, a 1:1 mixture of LysoPC and oleic acid induces an early increase, followed by an inhibition of both evoked and spontaneous neurotransmitter release. This effect is also induced by LysoPC alone. The present findings provide an indirect evidence that the lipid hemifusion-to-pore transition is a key event in neuroexocytosis in Drosophila. Moreover, these findings substantiate the use of LysoPC as a general agonist of membrane fusion at nerve terminals. This novel tool could contribute to the unraveling of the molecular steps involved in neuroexocytosis, particularly in Drosophila, where it is straightforward to combine it with electrophysiology and genetics
Active-site mutagenesis of tetanus neurotoxin implicates Tyr-375 and Glu-271 in the metalloprotease activity
No full textIF 2.00
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