1,721,030 research outputs found
The lead amalgam/lead sulfate electrode redesigned and reassessed
No full textTo make the (Pb)Hg|PbSO4|SO42- electrode really usable and attractive for extensive application in thermodn. studies, a new, simplified design and a convenient preparative procedure are introduced, ensuring stable amalgams and reproducible electrode potentials. The electrode thus prepd. was exhaustively characterized both thermodynamically and as a SO42- sensing electrode, in different sulfate solns., including H2SO4. The past discrepancies of std. potentials (mainly due to prepn. and/or handling problems) are discussed and, for a final resoln. of the question, a practical standardization procedure is proposed
An 8.5-kDa ribonuclease from the extreme thermophilic archaebacterium Sulfolobus solfataricus
No full textAbstractProtein p3, a ribonuclease we previously isolated from the archaebacterium Sulfolobus solfataricus [P. Fusi et al. (1993) Eur. J. Biochem. 211, 305–310], was subjected to complete amino acid sequencing. It consisted of 75 residues, with a calculated Mr of 8582, a pI of 10.1, and had some degree of monomethylation at Lys-4 and Lys-6. p2, a previously sequenced, 62-residue ribonuclease from the same organism, had an identical sequence for 57 consecutive residues starting from the N-terminus. p2 and p3 also showed a striking similarity to five other proteins previously isolated from Sulfolobus strains and identified as DNA-binding proteins. However, the C-terminus, 10 residue region of p3 did not show any similarity to these proteins; in contrast, it was significantly similar to stretches in three eubacterial ribonucleases from Bacillus strains. No difference between p2 and p3 has so far been detected as regards their catalytic properties. Available data suggest that these molecules have a narrow substrate specificity and probably play specific roles in RNA processing
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
Thermodynamic study of the aqueous (KCl + K2SO4) electrolyte based on potassium amalgam electrode cells
No full textThe thermodynamic behavior of the aqueous KCl + K2SO4 electrolyte has been studied on the basis of potential difference measurements on the reversible cell K-amalgam|KCl (mKCl) + K2SO4 (mK2SO4) |AgCl|Ag|Pt. The mean molal activity coefficients γKCl of KCl at molalities mKCl and γK2SO4 of K2SO4 at mK2SO4 in (KCl + K2SO4) mixtures have been determined at various constant values of total ionic strengths I of the mixed electrolyte studied. It has been found that log(γKCl) is a linear function of mKCl at each constant ionic strength studied, thus obeying Harned's rule. The corresponding trace activity coefficients, γ(0)KCl. vary linearly with log I. Using Pitzer's scheme of equations has allowed fair reproduction of the experimental activity coefficients γKCI for I values ≥ 0.5 mol·kg-1 and the evaluation of γK2SO4 in the same range
Characterization of a new bioadhesive material from fish parasites by a proteomic approach
No full textMonogenoids are fish parasites which are able to quickly and reversibly attach to their host through the secretion of a proteic glue. Unlike most adhesive secretions found in the animal world which stick to abiotic substrates, monogenoidean adhesive secretion works on living tissues. Moreover, the adhesion of the parasite to its host takes place in an aqueous environment, in the presence of strong water currents. All these features make it a very promising material for exploitation in the surgical field. Another unique and very interesting feature of monogenoidean adhesion is that it can be easily reverted through the secretion of a still uncharacterized “detaching” protein (S3), likely a protease. The adhesive secretion is produced by glands located besides the pharynx or more specifically, in the antero-lateral region of the animal. Demonstration of the proteinaceous nature of the glue came in 2002 (Hamwood TE et al., Folia parasitologica; 49(1):39-49) who showed that the material is SDS insoluble without any trace of glycosylation. No further characterization of the adhesive proteins has been performed since this initial report. Besides very promising potential clinical applications, the study of these proteins represents something completely new also from the biochemical point of view. Understanding the structure of these adhesive proteins, the way they combine to yield the insoluble glue working in an aqueous environment and the mechanism of interaction with a biological substrate, like an epithelium, represents a major challenge which will widen our knowledge about protein structure/function relationship. The aim of this work is the characterization of the bio-adhesive material by means of a proteomic approach. The first step of the project was to set up the conditions to obtain and solubilise the secreted material before separation by electrophoresis and characterization by tandem mass spectrometry.
OBTAINING THE SECRETED ADHESIVE MATERIAL
The secreted material was obtained by electrostimulation of the parasites in a 50% PBS solution using 40 volts electric field and 2 Hz frequency. The secretion of 30 parasites was collected in a test tube and the SDS soluble components were discharged. The remaining material was solubilised in buffer A (7M Urea, 2M Tiourea, 4% Chaps, 40mM TrisHCl). Upon sonication and centrifugation the supernatant was collected and the protein content was evaluated measuring the absorbance at 280 nm before electrophoresis.
PROTEIN SEPARATION BY 2D ELECTROPHORESIS
The proteins soluble in buffer A were separated by 2-D electrophoresis upon reduction and derivatization by iodoacetamide. Isoelectric focusing (IEF) was performed in 7 cm immobilised pH gradient (IPG) strips with non linear pH ranges of 3-10. The second dimension was performed on 12% SDS-polyacrylamide gels using a Mini Protean cell. Running proceeded at 20 mA/gel. After running, the 2-D gels were stained with a mass-compatible silver.
TANDEM MASS SPECTROMETRY AND DE NOVO SEQUENCING
For mass analysis, each spot was excised, destained with 50% acetonitrile in ammonium bicarbonate 0.1 M (40 min at 25 °C), dried in a Speed Vac, soaked with ammonium bicarbonate 0.1 M and digested overnight with trypsin sequencing grade (Roche, Monza, Italy) at 37 °C. The in gel tryptic digest was extracted with 50% acetonitrile in 0.1% trifluoroacetic acid. Digested aliquots were removed and subjected to a desalting/concentration step on a μZipTipC18 (Millipore) using 40% CH3CN in 0.1% TFA as eluent. LC-ESI-MS/MS analysis was performed on a Dionex UltiMate 3000 HPLC System with a Hypersil Gold column (150 mm, internal diameter of 180 μm) filled with 3μm Reprosil-Pur C18-AQ resin. The gradient consisted of 5-15 % acetonitrile in 0.1% formic acid for 10 min, 15-40% acetonitrile in 0.1% formic acid for 52 min and 40-95 % acetonitrile in 0.1% formic for 68 min at a flow rate of 1.2 μl/min . The eluate was electrosprayed into an LTQ Orbitrap Velos (Thermo Fisher Scientific, Bremen, Germany) through a Proxeon nanoelectrospray ion source for de novo sequencing since the genome of these parasites is still unknown. Tandem mass spectrometry analysis was performed with each full scan (400-1700 m/z) followed by 5 data-dependent MS/MS scan at 35% normalized collision energy. The full scans were acquired with 2-microscan averaging at resolution 30000, AGC target 500000, maximum inection time 500 ms. All MS/MS data were analyzed with the Sequest program and the Peak Studio 5.1 program
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
Problems in assesments of amalgam electrodes for standardising or certifying the corresponding ion selective electrodes
No full textThe primary method for standardizing or certifying an Mz+-ISE (Ion Selective Electrode for Mz+, where Mz+ = alkali or alkaline-earth cation) implies comparing the latter with the corresponding M-Amalgam electrode in the cell Pt|M-Amalgam|Mz+ Solution|M z+-ISE|Pt, whose potential difference is obviously independent of, Mz+ concentration. Assessment of the potential of the M-Amalgam electrode requires the precise determination of the mole fraction x of the M metal in amalgam, which is customarily performed by decomposing an M-Amalgam sample in excess HCl and titrating the HCl excess with standard NaOH solution. There arises the problem of choosing the correct end-point in pH-metric titrations of strong acids with carbonate-contaminated NaOH standard solutions, which is of frequent occurrence both in research and routine laboratory practice. This topic is either overlooked or insufficiently treated in textbooks: thus the interpretation of the above experimental pH-metric titration curves is often misled and the results may be affected by significant errors. Some recent misleading suggestions are here re-analyzed critically in order to focus correct, recommended methodological schemes
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
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