1,720,977 research outputs found
Bohr effect in hemoglobin deoxy/cyanomet intermediates
No full textThe Bohr protons released by oxygen exposure of the unliganded subunits of intermediates (α+CN-β)(α+CN-β) and (αβ+CN-)(αβ+CN-) were obtained by titrations of concentrated solutions of these species. The Bohr protons released by oxygen exposure of the other intermediates were obtained from titrations of equilibrium mixtures of two parental species, (αβ)(αβ), (α+CN-β)(α+CN-β), (αβ+CN-)(αβ+CN-), and (α+CN-β+CN-)(α+CN-β +CN-), in which the concentration of the hybrid intermediate was determined by cryogenic electrophoretic techniques. The Bohr effect of the intermediates was calculated by subtracting the Bohr protons released by oxygen exposure of the intermediates from the total Bohr protons of deoxyhemoglobin at the same pH. The Bohr effects of intermediates (α+CN-β)(αβ) and (αβ+CN-)(αβ) were similar and vanished at pH 8 where the total Bohr effect of deoxyhemoglobin is still significant. This suggests that the Bohr effect in these intermediates is tertiary in the quaternary T structure. The curve of the Bohr effect of intermediate (α+CN-β+CN-)(αβ), which was close to the curve obtained by adding the Bohr effects of the two monoliganded intermediates at acidic and physiological pH values, was significantly different from the curve obtained by adding the Bohr effects of one liganded subunit of intermediate (α+CN-β) (α+CN-β) and one liganded subunit of intermediate (αβ+CN-) (αβ+CN-). The Bohr effect of intermediate (α+CN-β)(αβ+CN-) was not determined, but the Bohr protons released by oxygen exposure of the equilibrium mixture of this intermediate and the parental species (α+CN-β)(α+CN-β) and (αβ+CN-)(αβ+CN-) suggest independent contributions to the Bohr effect of intermediate (α+CN-β)(αβ+CN-) from the Bohr effects of one liganded subunit of each parental species. These findings focus on the functional and structural asymmetry of thediliganded intermediates (α+CN-β+CN-)(αβ) and (α+CN-β)(αβ+CN-), which is predicted by the energetics of the same species [Smith, F. R., & Ackers, G. K. (1985) Proc. Natl. Acad. Sci. U.S.A. 82, 5347-5351; Perrella, M., et al. (1990) Biophys. Chem. 35, 97-103; Daugherty, M. A., et al. (1991) Proc. Natl. Acad. Sci. U.S.A. 88, 1110-1114]. The triply-liganded intermediates retained a significant Bohr effect up to physiological pH. The curve of the Bohr effect of intermediate (α+CN-β+CN-)(α+CN-β) was different from the curve calculated by adding the Bohr effects of intermediate (α+CN-β)(α+CN-β) and one liganded β subunit of intermediate (αβ+CN-)(αβ+CN-). Similarly the curve of the Bohr effect of intermediate (α+CN-βCN-)(αβ+CN-) was different from the curve calculated by adding the Bohr effects of intermediate (αβ+CN-)(αβ+CN-) and one liganded α subunit of intermediate (α+CN-β)(α+CN-β). This suggests that the tertiary structures of the liganded subunits in intermediates (α+CN-β)(α+CN-β) and (αβ+CN-)(αβ+CN-) and the triply-liganded intermediates are different, despite the energetics, which indicates that all these species are in the quaternary R structure
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
The Bohr effect of hemoglobin intermediates and the role of salt bridges in the tertiary/quaternary transitions
No full textUnderstanding mechanisms in cooperative proteins requires the analysis of the intermediate ligation states. The release of hydrogen ions at the intermediate states of native and chemically modified hemoglobin, known as the Bohr effect, is an indicator of the protein tertiary/quaternary transitions, useful for testing models of cooperativity. The Bohr effects due to ligation of one subunit of a dimer and two subunits across the dimer interface are not additive. The reductions of the Bohr effect due to the chemical modification of a Bohr group of one and two alpha or beta subunits are additive. The Bohr effects of monoliganded chemically modified hemoglobins indicate the additivity of the effects of ligation and chemical modification with the possible exception of ligation and chemical modification of the alpha subunits. These observations suggest that ligation of a subunit brings about a tertiary structure change of hemoglobin in the T quaternary structure, which breaks some salt bridges, releases hydrogen ions, and is signaled across the dimer interface in such a way that ligation of a second subunit in the adjacent dimer promotes the switch from the T to the R quaternary structure. The rupture of the salt bridges per se does not drive the transition
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
Functional heterogeneity of the alpha and beta subunits in the association reaction between hemoglobin and carbon monoxide
No full textA technique is described for the rapid inactivation and removal of excess ferricyanide used for the non-cryogenic oxidation of the unliganded subunits of the intermediates in the association reaction between hemoglobin and carbon monoxide. Under these conditions the asymmetric oxidized intermediates, which dissociate into non-identical dimers, disproportionate into their parent tetramers and four species, Hb+, HbCO, alpha 2+ beta 2CO, alpha 2CO beta 2+, are isolated by non-cryogenic isoelectric focusing. The relative concentrations of species alpha 2CO beta 2+ and alpha 2+ beta 2CO measure the overall distribution of the ligand between the alpha and beta subunits in the association reaction. At 20 degrees C in 0.1 M KCl, pH 7, preferential CO binding to the beta subunits was observed, in agreement with observations made by the cryogenic technique for the isolation of the intermediates [M. Perrella, N. Davids and L. Rossi-Bernardi, J. Biol. Chem. 267 (1992) 8744]
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
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