1,720,976 research outputs found
Metal co-ordination, protein-folding, and electron-transfer studies of wild-type and mutant azurin
No full textAzurin is a copper-containing protein that functions as an electron carrierin certain bacteria. Like other cupredoxins its three-dimensional structureis essentially that of a b-barrel. The interaction between the oxidizedcopper ion and the metal binding site of the protein results in a strongoptical absorption around 630 nm and a special combination of EPRparameters. The copper ion in azurin is co-ordinated by three strongligands (NNS) and two more weakly interacting groups (S and O).The properties of the metal binding site in azurin have been probed byreplacing the native copper ion for non-native cobalt and nickel ions, andthe resulting structures have by X-ray crystallography been determined. Themain difference compared to copper is a displacement of cobalt and nickeltoward the oxygen ligand. This makes these metal ions four co-ordinated.Spectroscopic and structural properties of the copper ion in azurin havealso been probed by binding small molecules to the metal. These moleculesinteract with the copper ion in 121X azurin mutants, but not in wild-typeazurin. The interaction of the mutants M121X (X = Gly, Ala, Val, Leu, andAsp) with oxygen- and nitrogen-containing ligands has been analyzed by EPRand optical spectroscopy, as well as by resonance Raman spectroscopy. TheX-ray structure of Ala121 and Ala121 + azide have been determined in orderto analyze the geometrical changes upon ligand binding. One end of theexogenous ligand azide interacts with the copper ion close to where thesulfur of Met121 is positioned in the wild-type structure. This structuredemonstrates that the exogenous ligand interaction can change theco-ordination of the copper ion from three to four strong ligands.The effect of removing the disulfide bond in azurin has been investigated.The major change upon replacing the cysteine residues in the disulfide bondfor alanine residues is a decreased folding stability. It is concluded thatthe disulfide contributes at least 20 kJmol-1 to the folding energy ofazurin.A possible function of aromatic amino acids in the electron transferreaction has been investigated by introducing an additional tryptophan inazurin. The tryptophan was engineered in a proposed electron transferpathway in van der Waals contact with the native tryptophan. Evidencesuggests that several aromatic amino acids stacked against each other mayinduce a more effective electron transfer between the donor and acceptorsite
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Optimizing yeast as a host for recombinant protein production
No full textHaving access to suitably stable, functional recombinant protein samples underpins diverse academic and industrial research efforts to understand the workings of the cell in health and disease. Synthesizing a protein in recombinant host cells typically allows the isolation of the pure protein in quantities much higher than those found in the protein's native source. Yeast is a popular host as it is a eukaryote with similar synthetic machinery to the native human source cells of many proteins of interest, whilst also being quick, easy and cheap to grow and process. Even in these cells the production of some proteins can be plagued by low functional yields. We have identified molecular mechanisms and culture parameters underpinning high yields and have consolidated our findings to engineer improved yeast cell factories. In this chapter we provide an overview of the opportunities available to improve yeast as a host system for recombinant protein production
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe 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
Get PDFWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
- …
