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Exon 26-coded polypeptide: An isolated hydrophobic domain of human tropoelastin able to self-assemble in vitro
No full textHydrophobic domains of human tropoelastin are able to aggregate in a variegated manner. Some aggregates have typical features of the whole protein while others show peculiar self-assembling profiles. Among these hydrophobic domains, an important role in the self-assembling properties of tropoelastin in vitro could be assigned to the peptide encoded by exon 26 of the human tropoelastin gene, that, although unstructured in solution, has great tendency to self-assemble in an ordered manner. The present report describes the aggregation properties of this hydrophobic domain of human tropoelastin analysed by different ultra-structural approaches. Transmission electron microscopy shows that the peptide is able to form different aggregation entities from short rods to very long and flexible fibers, depending on the temperature and on the incubation time. At a μm scale, very long fibers as well as fractal aggregation patterns were observed. Data show that the isolated domain encoded by exon 26 of the tropoelastin gene is able to aggregate in a manner very similar to the whole tropoelastin protein. The aggregation properties are due to the peculiar sequence of EX26, and not to its amino acid composition, as evidenced by the supramolecular analysis of a scrambled sequence of exon 26-coded domain of human tropoelastin, showing a quite different aggregation patterns.
These findings confirm that specific sequences can play a driving role in the aggregation process of tropoelastin molecule, at least in vitro, and indicate exon 26-encoded domain among these sequences
Amyloid organization of elastin-based biopolymers: an XPS and AFM study, EMBO-FEBS workshop on Amyloid formation, Florence, Italy, 25-28 March (2006)
No full text
Conformational study and Hydrogen bonds detection on Elastin-related poly-peptides using X-ray Photoelectron Spectroscopy, XPS
No full textThe chemical bonds of the pentapeptide sequence of elastin ValGlyGlyValGly (VGGVG), both in its monomer and polymer forms, were correlated with their XPS spectra through a well-established curve-fitting procedure. To aid in this correlation, the C1s, O1s, and N1s chemical shifts of the Boc-VGGVG-OEt, were validated by theoretical calculations, performed in the framework of the Koopman approximation of HF/6-31G molecular orbitals, leading to the "preferred" conformation of the protected monomer. Then the same curve-fitting procedure was adopted for interpreting the XPS spectra of the polypentapeptide as a powder, and the XPS results obtained both for monomer and polymer compounds were compared with those obtained by FT-IR. The polymer was then analyzed after deposition onto a silicon substrate, Si(100), either from methanol or water suspensions and the presence of hydrogen bonds was detected at the polymer/substrate interface and between the polymer chains. The "surface rearrangement" that could be inferred from XPS results strongly confirms that derived from AFM images previously obtained under the same experimental conditions. In particular, the observed amyloid conformation is stabilized by hydrogen bonds to water molecules included in the structure while the formation of the beaded string structure observed in deposits from methanolic suspension is probably mediated by hydrogen bonds to the hydrated silicon surface
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
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