1,720,979 research outputs found
Dissection of human tropoelastin: solution structure, dynamics and self-assembly of the exon 5 peptide
No full textThe elastic properties of elastin have essentially been discussed in terms of dominant entropic components, with questions still remaining about whether the basic mechanism is compatible with the classical theory of rubber elasticity. A better understanding of the structure-function relationships in terms of the protein's elastic properties remains an important goal in elastin science. Recently, we succeeded in the exon-by-exon synthesis of all polypeptide sequences encoded by the so-called hydrophobic exons and almost all of the cross-linking exons of human tropoelastin. Among these, the peptide encoded by exon 5 (PGGLAGAGLGA) has been extensively studied by classical spectroscopic methods, such as CD and NMR spectroscopy, and by molecular dynamics simulations. The results obtained clearly evidenced a large flexibility of the polypeptide chain, which oscillates between rather extended conformations, such as PPII, and folded ones, such as beta turns. At the supramolecular level, we obtained evidence by TEM that shows that the peptide encoded by exon 5 is able to self-assemble in fibrillar structures, a result indicating that the "information" for self-assembly is also contained within a small domain of tropoelastin
Interaction of elastin derived peptides with the SGAL peptide, a domain of the elastin-binding protein
No full textStructure and modeling studies of the carboxy-terminus region of human tropoelastin.
No full textElastin macromolecular assembly is a highly complex mechanism involving many steps including coacervation, cross-linking, and probably other (not known) phenomena. In past studies, it has been proposed that the C-terminal part of tropoelastin is also involved in this process and may play a key role in tropoelastin interactions with other proteins of the final elastic fibres scaffold. Presented here are the results of the biophysical studies (biospectroscopy, bioinformatics) of the C-terminal domain of tropoelastin. We report the detailed structures adopted by the oxidized (native) and reduced forms of the free synthetic peptide with sequence encoded by exon 36 of human tropoelastin (GGACLGKACGRKRK) and propose a dynamical interpretation of which structures may be involved in interactions with other extra-cellular matrix proteins. We also suggest that these structures may be retrieved in other proteins sharing a consensus sequence; however no definitive conclusion can be drawn here on a possible structure-function relationship
Spectroscopic and Theoretical Characterisation of the type VIII beta-turn. Study of the tetrapeptide GDNP
No full textSpectroscopic evidence revealing polyproline II structure in hydrophobic, putatively elastomeric sequences encoded by specific exons of human tropoelastin.
No full textElastin, the protein responsible for tissue elasticity, is contained in arterial walls, lungs, and skin. Given the cassette like organization of the human tropoelastin gene, giving rise to alternating exons encoding for crosslink domains and elastomeric domains, it is tempting to suggest that polypeptides encoded by different exons could adopt structures independent of the other exons. The results obtained with the polypeptide sequences encoded by exons 3, 7, and 30 of human tropoelastin are described. It is shown that these hydrophobic exons may partly assume the polyproline II (PPII) structure, as found by circular dichroism studies in aqueous solution. Classical Raman spectroscopy evidences a specific sharp band at 1314 cm(-1), which is assigned to the PPII structure adopted by these exons in the solid state. As these sequences are among those putatively responsible for elastomeric properties, these findings are of particular interest in relation to the current models of the elasticity of elastin
A proposed interaction mechanism between elastin derived peptides and the elastin/laminin receptor binding domain
No full textElastin-derived peptides (EDPs) have been
intensively studied in view of their widely
diverse biological activities. These are
triggered both in normal and tumor cells,
through peptide anchoring at the surface
of the elastin-binding protein (EBP), a
subunit of the elastin/laminin receptor. In
this study, we investigated both the structure
of the Sgal peptide, representing the
elastin-binding domain of EBP, and its
interaction with EDPs, through a combination
of experimental and theoretical
methods. Although the conformation of
the Sgal peptide is highly flexible, we
detected a type I b-turn at the QDEA
sequence. This represents the best structured
motif in the entire Sgal peptide,
which might therefore contribute to its
binding activity. We further propose a
novel three-dimensional model for the
interaction between the Sgal peptide and
EDPs; folding of the EDPs at the GXXP
motif, in a conformation close to a type
VIII b-turn, provides the efficient contact
of the protein with the Q residue of the
Sgal peptide. This residue is exposed to
the peptide surface, because of the b-turn
structure of the QDEA residues in the
peptide sequence. We further show that
this complex is stabilized by three hydrogen
bonds involving EDPs backbone
atoms
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
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
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