1,720,963 research outputs found
THE REACTION OF OCTOPUS-VULGARIS HEMOCYANIN WITH EXOGENOUS LIGANDS - PROPOSAL OF AN ALLOSTERIC MODEL FOR THE BINDING OF CYANIDE AND THIOUREA TO THE 11-S SUBUNIT
No full textSaccharose solid matrix enbedded proteins: a new method fro XAS sample preparation
No full texti.f. 1,950; biophysic
LUMINESCENCE PROPERTIES OF THE DINUCLEAR COPPER COMPLEX IN THE ACTIVE-SITE OF HEMOCYANINS
No full textThe deoxygenated form of hemocyanin, containing a dinuclear Cu(I) active site, emits luminescence in the red with maximum around 1.54 mu m(-1) (650 nm). The luminescence of deoxyhemocyanin (deoxy-Hc) from arthropod species is detectable at room temperature, the quantum yield being 2.4-2.7 X 10(-3); in contrast, the emission from molluscan proteins can be detected only at liquid nitrogen temperature. The luminescence emission is an inherent property of the bis[Cu(I)-(histidine)(3)] complex of the deoxygenated form of the protein to which both Cu(I) ions contribute equally to the overall emission. Luminescence is not observed with the oxygenated and the oxidized forms of hemocyanin, in which the metal is in the Cu(II) state, and in the metal-depleted or apo-Hc form. Based on steady-state and time-resolved measurements and references to Cu(I) model compounds, the luminescence emission is attributed to a triplet excited state of a Cu(I)-to-N (histidine) charge transfer transition (3)d-pi*. Acrylamide quenching experiments indicate that the metal active site is very shielded from the solvent. This property of deoxy-Hc enables us to directly follow reactions that modify either the copper oxidation number or the metal-to-protein stoichiometry
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
Functional SAXS study of haemocyanin dioxygen-carrier protein
No full textThe effects of conformational rearrangements on dioxygen binding to molluscan haemocyanins have been investigated by small-angle X-ray scattering (SAXS), The SAXS patterns of the oxygenated and deoxygenated forms of Octopus vulgaris haemocyanin are significantly different; whereas the patterns of the two forms of Rapana thomasiana haemocyanin are almost superimposable. A program has been developed, based on the differences in molecular dimensions, in order to simulate the effects observed in the investigation
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
SAXS ON INVERTEBRATE DIOXYGEN CARRIERS
No full textSome preliminary SAXS measurements have been carried out on four different extracellular invertebrate dioxygen carriers. The validity of the procedure has been tested on arthropod hemocyanin: the radii of gyration deduced from SAXS spectra agree with those calculated from the dimensions of the structure determined by X-ray crystallography. The radii of gyration of Spirographis spallanzanii chlorocruorin agrees with values deduced from 3D structures obtained with Electron Microscopy. The radius of gyration and the radius of the cross section of Octopus vulgaris hemocyanin are compatible with a ring structure, as deduced from investigations made by Electron Microscopy
The use of small-angle X-ray scattering in the study of quaternary organisation of giant proteins
No full textWe report an investigation on the quaternary organisation of hemocyanin giant proteins, performed with continuous small-angle X-ray scattering (SAXS) at the LURE facility. The molecular weight of a 11S subunit of molluscan hemocyanin was determined from the experimental data. Structural models of this subunit, which include seven or five functional units, were also derived and correlated to the whole molecule, which has the form of a hollow cylinder
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