1,721,001 research outputs found
SDS-PAGE patterns of whole cell proteins of Streptococcus thermophilus: impact of strain, growth phase and adaptation and relationship with stress response
No full textIn previous studies we demonstrated that a relatively large diversity of stress response patterns (acid, osmotic, oxidative, heat) exists among Streptococcus thermophilus strains. Changes in protein expression, evaluated by SDS–PAGE in 4 wild strains (CNBL7035, TH681, Y3, Sfi39) and in three Sfi39 mutants in which hrcA, ctsR and rr01 genes were inactivated showed that significant variations of proteins involved in general stress response (GSR) occur as a function of growth phase, adaptation and inactivation of stress response regulators. In this work we re-evaluate the previous results comparing two unsupervised (Hierarchical Cluster Analysis, HCA, and Principal Component Analysis, PCA) and one supervised (Partial Least Square Regression, PLSR) statistical techniques for the ability to extract information from SDS–PAGE patterns of wild type and mutant strains of S. thermophilus and to uncover relationships between protein patterns and stress tolerance. HCA and PCA are two purely descriptive techniques. The HCA showed that SDS–PAGE is an efficient tool to differentiate strains but did not shed any light on the relationships between band intensity and strain, growth phase or adaptation treatment. PCA helped to identify group of bands which covaried with the stress input factors butalso not allow to find a relationship between protein expression and stress tolerance. The PLS regression, even with the limitations due to the data set used in this study, appears as an extremely promising tools for the identification of complex relationships between design and response variables in the analysis of SDS–PAGE patterns of whole cell proteins
Membrane topology analysis of the Bacillus subtilis BofA protein involved in pro-sigma(K) processing
No full textThe Bacillus subtilis BofA protein is involved in regulation of pro-σ(K) processing in the mother cell during the late stages of sporulation. A computer analysis of the BofA amino acid sequence indicates that it is an integral membrane protein. To determine the membrane topology of the protein, a series of gene fusions of bofA with lacZ or phoA reporter genes in Escherichia coli were analysed. A BofA topological model with two membrane-spanning segments, and with the N- and the C-terminal domains located in the region between the inner and outer membranes surrounding the forespore is presented. The analysis of different modifications of the last five amino acid residues of the BofA protein, obtained by PCR site-directed mutagenesis, suggests a possible role of the C-terminal domain in the regulation of pro-σ(K) processing
A new Bacillus subtilis gene with homology to Escherichia coli prc
No full textWe report the cloning of a 2-kb PstI-BamHI fragment of Bacillus subtilis DNA carrying an open reading frame of 1398 bp, herein designated orfRM1. This orf was shown to be transcribed only during vegetative growth from a putative o(A)-specific promoter. The deduced amino acid sequence predicted a polypeptide of 51 kDa (466 aa), which shows significant percentage of identity with the Escherichia coli Prc protein. However no Prc-like phenotypes were observed in a B. subtilis orfRM1 deletion-insertion mutant
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
Expression of the bglH gene of Lactobacillus plantarum is controlled by carbon catabolite repression
No full textA newly identified bglH gene coding for a phospho-β-glucosidase of Lactobacillus plantarum was isolated and expressed in Escherichia coli. The sequence analysis of the cloned DNA fragment showed an open reading frame encoding a 480-amino-acid protein with a calculated molecular mass of 53 kDa. The bglH gene was shown to be expressed on a monocistronic transcriptional unit. Its transcription was repressed 10-fold in L. plantarum cells grown on glucose compared to the β-glucoside salicin as a sole carbon source. A catabolite-responsive element (CRE) spanning from -3 to ±11 with respect to the transcriptional start point was found, and its functionality was assessed by mutational analysis. In vitro and in vitro DNA binding experiments suggested the occurrence of a DNA-protein complex at the CRE site, which would mediate glucose repression of bglH expression
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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