1,720,990 research outputs found
A novel rhamno-mannan exopolysaccharide isolated from biofilms of Burkholderia multivorans C1576
No full textBurkholderia multivorans C1576 is a Gram negative opportunistic pathogen causing serious lung infection in cystic fibrosis patients. Considering that bacteria naturally form biofilms, and exopolysaccharides are recognized as important factors for biofilm architecture set-up, B. multivorans was grown both in biofilm and in non-biofilm mode on two different media in order to compare the exopolysaccharides biosynthesized in these different experimental conditions. The exopolysaccharides produced were purified and their structure was determined resorting mainly to NMR spectroscopy, ESI mass spectrometry and gas chromatography coupled to mass spectrometry. The experimental data showed that both in biofilm and non-biofilm mode B. multivorans C1576 produced a novel exopolysaccharide having the following structure: [Formula: see text]. About 50% of the 2-linked rhamnose residues are substituted on C-3 with a methyl ether group. The high percentage of deoxysugar Rha units, coupled with OMe substitutions, suggest a possible role for polymer domains with marked hydrophobic characteristics able to create exopolysaccharide junction zones favouring the stability of the biofilm matrix
Determination of the capsular polysaccharide structure of the Klebsiella pneumoniae ST512 representative strain KPB-1 and assignments of the glycosyltransferases functions
Full text linkKlebsiella pneumoniae strain KPB-1 was isolated in early 2011 from the pleural fluid of an inpatient admitted at an Italian hospital. It was characterized to produce the KPC-3 carbapenemase and to belong to sequence type 512, a derivative of sequence type 258 clade II characterized by the cps-2 gene cluster. The K-antigen of K. pneumoniae KPB-1 was purified and its structure determined by using GLC-MS of appropriate carbohydrate derivatives and 1D and 2D NMR spectroscopy of the native polysaccharide. All the collected data demonstrated the following repeating unit for the K. pneumoniae KPB-1 capsular polysaccharide: The reactions catalysed by each glycosyltransferase in the cps-2 gene cluster were assigned on the basis of structural homology with other Klebsiella K antigens
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
Characterisation of a new cell wall teichoic acid produced by Listeria innocua ŽM39 and analysis of its biosynthesis genes
Full text linkListeria innocua is genetically closely related to the foodborne human pathogen Listeria monocytogenes. However, as most L. innocua strains are non-pathogenic, it has been proposed as a surrogate organism for determining the efficacy of antimicrobial strategies against L. monocytogenes. Teichoic acids are one of the three major cell wall components of Listeria, along with the peptidoglycan backbone and cell wall-associated proteins. The polymeric teichoic acids make up the majority of cell wall carbohydrates; the type of teichoic acids directly attached to the peptidoglycan are termed wall teichoic acids (WTAs). WTAs play vital physiological roles, are important virulence factors, antigenic determinants, and phage-binding ligands. The structures of the various WTAs of L. monocytogenes are well known, whereas those of L. innocua are not. In the present study, the WTA structure of L. innocua ŽM39 was determined mainly by 1D and 2D NMR spectroscopy and it was found to be the following: [→4)-[α-D-GlcpNAc-(1→3)]-β-D-GlcpNAc-(1→4)-D-Rbo-(1P→]n This structure is new with respect to all currently known Listeria WTAs and it shares structural similarities with type II WTA serovar 6a. In addition, the genome of strain L. innocua ŽM39 was sequenced and the majority of putative WTA synthesis genes were identified
Effect of o-antigen chain length regulation on the immunogenicity of shigella and salmonella generalized modules for membrane antigens (GMMA)
Full text linkRecently, generalized modules for membrane antigens (GMMA) technology has been pro-posed as an alternative approach to traditional glycoconjugate vaccines for O-antigen delivery. Saccharide length is a well-known parameter that can impact the immune response induced by glycoconjugates both in terms of magnitude and quality. However, the criticality of O-antigen length on the immune response induced by GMMA-based vaccines has not been fully elucidated. Here, Shigella and Salmonella GMMA-producing strains were further mutated in order to display homogeneous polysaccharide populations of different sizes on a GMMA surface. Resulting GMMA were compared in mice immunization studies. Athymic nude mice were also used to investigate the involvement of T-cells in the immune response elicited. In contrast with what has been reported for traditional glycoconjugate vaccines and independent of the pathogen and the sugar structural characteristics, O-antigen length did not result in being a critical parameter for GMMA immunogenicity. This work supports the identification of critical quality attributes to optimize GMMA vaccine design and improve vaccine efficacy and gives insights on the nature of the immune response induced by GMMA
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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