1,720,967 research outputs found
Analisi struttura-funzione dell’apirasi, proteina associata alla virulenza prodotta da shigella e da ceppi di Escherichia coli enteroinvasivi
No full textAla160 and His116 residues are involved in activity and specificity of apyrase, an ATP-hydrolysing enzyme produced by enteroinvasive Escherichia coli
No full textThe virulence plasmid-carried apy (phoN2) gene of Shigella and related enteroinvasive
Escherichia coli (EIEC) encodes apyrase, an ATP-diphosphohydrolase belonging to class A
of the non-specific acid phosphatases (A-NSAPs). Apyrase and A-NSAPs share three domains
of conserved amino acids (domains D1–D3) containing residues forming the putative active site of
apyrase. In spite of their similarity, apyrase and A-NSAPs show different substrate specificity,
apyrase being able to hydrolyse nucleotide tri- and diphosphates, but not monophosphates, as
well as p-nitrophenyl phosphate (pNPP), while A-NSAPs are also active towards monophosphates
and pNPP. In this paper, to get further insights into the structure–function relationship of apyrase, a
random and site-directed mutagenesis of the apy gene of EIEC strain HN280 was conducted.
Results indicate that amino acids located within the D2 and D3 conserved domains (Ser157 and
Arg192, respectively) as well as residues located in the N-terminal (Ser97) and C-terminal
(Glu233) domains are required for enzyme activity. Surprisingly, Ala160, located near the D2
domain and considered to be important for enzyme specificity, is required for enzyme activity, as its
substitution with Thr led to the inactivation of enzyme activity. Furthermore, residue His116 is
involved in apyrase specificity, since the H116L apyrase mutant shows substrate specificity
resembling that of A-NSAPs
Burkholderia cenocepacia vaginal infection of a patient with smouldering myeloma and chronic HCV infection: a case report
No full textEnteroinvasive Escherichia coli virulence plasmid-carried apyrase (apy) and ospB genes are organized as a bicistronic operon and are subjected to differentiated expression
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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
Prevalence of IgG antibodies against Borrelia burgdorferi SL and Ehrlichia phagocytophila in sera of patients presenting symptoms of Lyme disease in a central region of Italy
No full textThe aim of this study was to evaluate the prevalence (seroprevalence) of antibodies against Borrelia burgdorferi and Ehrlichia phagocytophila among patients resident in Lazio, a region of central Italy. Of a sample of 1,050 patients, which presented clinical manifestations related to Lyme disease, 34 (3.2%) were Borrelia-seropositive (Lyme index value greater than or equal to 1.2). The sera of 25 out of the 34 patients that were Borrelia-positive were also analysed for the presence of antibodies against E. phagocytophila and 3 (12%) were found Ehrlichia-positive (titres >1:64). No Ehrlichia-positive samples were found among sera of 250 Borrelia-negative patients. Since both B. burgdorferi s.l. and Ehrlichia species share the same tick vector (Ixodes ricinus), our results indicate that concurrent transmission of these microbial pathogens might have been occurred among the patients included in this study
Apyrase, the product of the virulence plasmid-encoded phoN2 (apy) gene of Shigella flexneri, is necessary for proper unipolar IcsA localization and for efficient intercellular spread
No full textThe role in virulence of the Shigella flexneri ospB-phoN2 operon has been evaluated. Here we confirm that OspB is an effector and show that apyrase, the product of phoN2, may be a virulence factor, since it is required for efficient intercellular spreading. Apyrase may be important in a deoxynucleoside triphosphate-hydrolyzing activity-independent manner, suggesting that it may act as an interaction partner in the process of IcsA localization
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