1,721,067 research outputs found
Multi-scale simulations of membrane active peptides: The fusion peptides
No full textIAP/Belspo P6/19 project - Proteins: interaction involved in folding, function and supramolecular assemblage
Contribution to the Study of Tilted Peptides Involved in Protein Transconforamtion
Get PDFThe study of the amyloidogenic proteins is important to understand the
transconformational processes. These proteins have a unique common feature : they undergo a
conformational change leading to the formation of highly structured fibrils that are mainly β
conformed. These proteins are difficult to study experimentally due to their low solubility and
their tendency to aggregate rapidly.
Recently, tilted peptides have been detected in such proteins. These peptides are short
fragments (11 to 18 residues) that adopt a tilted orientation when they interact with a
hydrophilic/hydrophobic interface. This property is due to the presence of an asymmetric
hydrophobicity gradient when they are helical. Those peptides are able to destabilize
organized molecular systems. Amyloidogenic proteins containing such peptides are the PrP
protein, the Aȕ peptide, and the bacterial prions Ure2p and Sup35p. The presence of such fragments in transconformational proteins has led to the
hypothesis that tilted peptides could be implied in the conformational change of
amyloidogenic proteins. These peptides could play a role through their destabilizing
properties and/or their structural lability.
The aim of this work was to detect tilted peptides among other amyloidogenic proteins
by molecular modelling. One of the detected peptides is tested experimentally to evidence its
lipid destabilizing properties. Five tilted peptides from four different proteins have been
detected among 27 amyloidogenic proteins. The tilted fragment from the α-synuclein
sequence, a protein involved in Parkinson disease, has been synthetized and tested for lipid
fusion. The fusogenic assays pointed out its destabilizing properties. These results support the
hypothesis that tilted peptides could be involved in transconformational processes.Etude de l’implication des peptides obliques dans les phénomènes de transconformatio
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
Detection and characterization of tilted peptides in amyloid proteins
Get PDFThe study of amyloidogenic proteins is of interest in biochemistry because these
proteins undergo conformational changes and aggregation. Both processes are largely
implicated in several diseases including Alzheimer’s, Parkinson’s or Creutzfeldt-Jakob’s
disease. These phenomena are not completely understood, either at a structural or energetical
point of view.
Tilted peptides are short protein fragment (11 to 19 residues) that adopt a tilted orientation
when inserted into biological membranes and destabilise them. Recently, tilted peptides have
been detected in two amyloidogenic proteins involved in neurodegenerative diseases; the
amyloid β peptide responsible for Alzheimer’s disease, and the PrP protein that causes
Creutzfeldt-Jakob’s disease.
Tilted peptides could be responsible for the neurotoxic effects of these proteins. Due to their
destabilising properties, they could interact directly with the membrane leading to cell death.
Tilted peptides could also be involved in the transconformational process of the proteins. The aim of this work is to detect tilted fragments in other amyloidogenic proteins by
molecular modelling and to study some of these peptides experimentally to evidence their
lipid destabilizing properties, their structure and their toxicity. In addition, this work enable
the design of an automatic method of detection for tilted peptides. Twenty-two tilted peptides
from 18 different proteins have been detected among 53 amyloidogenic proteins and 7
peptides were tested experimentally. The results support the hypothesis that some tilted
peptides could be involved in transconformational processes and/or cytotoxicity related to
amyloidogenic proteins.Etude de l’implication des peptides obliques dans les phénomènes de transconformatio
Experimental Study of the α-Synuclein Tilted Peptide
Get PDFThe study of amyloidogenic proteins is of great interest in biochemistry because these proteins undergo a conformational change and an aggregation, that are largely implicated in several incurable diseases including Alzheimer’s, Parkinson’s or Creutzfeldt-Jakob’s disease. In addition, these phenomena are not completely understood, either structurally or energetically. These proteins, in their amyloidogenic conformation, aggregate rapidly in solution and form fibrils that are insoluble and resistant to proteolysis.
Recently, tilted peptides were detected in two of the amyloidogenic proteins involved in neurodegenerative diseases; the amyloid β peptide responsible for Alzheimer’s disease, and the PrP protein that causes Creutzfeldt-Jakob’s disease. Tilted peptides are short protein fragments (11 to 18 residues) that adopt a tilted orientation when inserted into biological membranes, which they are able to destabilise. When helical, tilted peptides present an asymmetric hydrophobicity gradient responsible for their oblique insertion.
Tilted peptides have also been detected in some other amyloidogenic proteins. In a set of 27 amyloidogenic proteins, five tilted peptides from four different proteins have been shown up by molecular modelling. Tilted peptides could be responsible for the neurotoxic effect of these proteins. Thanks to their fusogenic properties, they could interact directly with the membrane leading to cell death. Tilted peptides could also be involved in the tranconformational process of these proteins.
The aim of this study was to characterise experimentally the tilted peptide detected by molecular modelling in the α-synuclein sequence, responsible for Parkinson’s disease. This peptide is tested experimentally to highlight its lipid destabilising properties. Its conformation is studied by IR spectroscopy. The fusogenic assays point to its destabilizing properties.Etude de l’implication des peptides obliques dans les phénomènes de transconformatio
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
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
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