1,721,124 research outputs found
Synthesis of a heterotrimeric triple helical „mini-collagen“ with a C-terminal disulfide knot for induction of the correct register.
No full textCopper binding and conformation of the N-terminal octarepeats of the prion protein in the presence of DPC micelles as membrane mimetic
No full textThe prion protein is usually pictured as globular structured C-terminal domain that is linked to an extended flexible N-terminal tail. However, in its physiol. form, it is a glycoprotein tethered to the cell surface via a C-terminal GPI anchor. The low soly. of PrP even without GPI anchor and its strong tendency for aggregation has forced most structural investigations to be performed at low pH and mostly with N-terminally truncated variants. In the present study, we have used a synthetic peptide related to the PrP tetra-octarepeat region, i.e., the sequence (Pro-His-Gly-Gly-Gly-Trp-Gly-Gln)4, for NMR structural anal. of its preferred conformation in DPC micelles as membrane mimic. Well-defined and identical loops are obsd. between the four octarepeats that are linked by flexible Gly-Gly-Gly sequences. Interaction with the micelles is mainly through the tryptophan residues that appear to act as anchors. Copper binding to the peptide in the presence of DPC micelles revealed marked conformational rearrangements although binding to the micelles is preserved. Interestingly, titrn. expts. point to cooperative effects for the four binding sites. A destabilization of the DPC micelles by the peptide parallels the destabilizing effect of the prion protein on membranes so that the octarepeat region appears to be very membrane-active. How the physico-chem. properties reported here are linked to the function and significance of the prion protein remains a puzzle as long as the functional mechanism of the prion protein is not precisely elucidated. Nevertheless, our results emphasize the strong influence of the (membrane) environment on the PrP properties
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
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
Spectroscopically labeled peptaibiotic analogs: the 4-nitrophenylalanine infrared absorption probe inserted at different positions into trichogin GA IV
No full textA set of three analogs of the 10-residue, membrane-active lipopeptaibiotic trichogin GA IV, labeled with the promising
4-nitrophenylalanine IR absorption probe for local polarity, was synthesized by the solid-phase methodology, chromatographically
purified, and extensively characterized. A single residue modification was inserted near the N-terminus, in
the central region, or at the C-terminus. A solution conformational analysis, carried out by FT-IR absorption, CD, and
2D-NMR combined with molecular dynamics calculations, indicates that the mono-labeled analogs maintain the overall
helical properties of the parent compound. Membrane permeabilization measurements and antimicrobial tests revealed
that they possess membrane-modifying properties and in vitro antibacterial activities analogous to those of the natural
lipopeptaibiotic. Our IR absorption and attenuated total reflectance investigations in various environments, from which
water was excluded for solubility reasons, showed that the 1350 cm1 4-nitrobenzyl band is a reporter group of rather
limited sensitivity
- …
