1,720,975 research outputs found
Crystal Structure of Liganded and Unliganded Forms of Bovine Plasma Retinol-Binding Proteins.
No full textCrystal Structure of Liganded and Unliganded Forms of Bovine Plasma Retinol-Binding Protein
No full textThe three-dimensional structures of bovine plasma retinol-binding protein (bRBP) complexed with retinol (space group P2(1)2(1)2(1), a = 46.08, b = 49.12, c = 76. 10 angstrom) and of the unliganded protein prepared in vitro by extracting retinol with ethyl ether (space group P2(1)2(1)2(1), a = 46.55, b = 48.97, c = 76.87 angstrom) have been solved at 1.9 and 1.7 angstrom resolution, respectively. The final crystallographic R factors are 0.190 for holobRBP and 0.196 for the unliganded bRBP.
The model for the bovine holoprotein is quite similar to that of the human protein, with which it exhibits 92% sequence similarity. The root mean square deviation between the alpha-carbons in the two proteins is 0.31 angstrom. The retinol binding site is almost completely preserved. The loops that surround the opening of the beta-barrel are also particularly conserved, in contrast with the presence of several substitutions in parts of the RBP molecule opposite the opening of the calyx that binds retinol.
Despite the fact that unliganded bovine RBP was prepared and crystallized using procedures completely different from those used to obtain the unliganded human RBP, the conformational differences between unliganded and liganded forms of bRBP are almost identical to those found previously between the same forms of human RBP. They mainly involve a few residues in the region extending from amino acid residues 32 to 37. Therefore, similar differences are very likely to exist between holoRBP and the physiologically occurring apoprotein. A not yet identified electron density, different in shape and orientation from retinol, also occupies the central cavity of the beta-barrel in the unliganded bRBP, as found for unliganded human RBP. The functional consequences of the conformational change induced by the removal of retinol on the interaction between RBP and transthyretin, coupled with the conservation of the entrance loops of the beta-barrel in mammalian RBPs, are consistent with their participation in molecular interactions
Experimental methods in X-ray and neutron crystallography
No full textCrystallography is an interdisciplinary science covering a wide area, from biology to earth sciences, mathematics and materials science. Its role is growing, owing to the contribution crystallography can offer to the understanding of such diverse fields as biological structures, high-temperature superconductors, mineral properties, and phase transitions. The book describes both the theoretical bases and applications of different areas interacting with crystallography. As with the first and second editions, it is organized as a collection of chapters written by recognized specialists, with all contributions being harmonized into a unified whole. The main text is devoted to the presentation of basics; the appendices deal with specialist aspects. In this third edition topics have been updated so as to document the present state of the art: emphasis is placed upon areas of current research
Crystal Structure of the Trigonal Form of Human Plasma Retinol-Binding Protein at 2.5 Å Resolution
No full text
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
Evaluation of quail egg white riboflavin binding protein as a chiral selector in HPLC and CE
No full textEgg yolk riboflavin binding protein as a new chiral stationary phase in high-performance liquid chromatography
No full text- …
