Solid-state studies on synthetic fragments and analogues of elastin (original) (raw)
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Molecular Mobility of Elastin: Effect of Molecular Architecture
Biomacromolecules, 2002
The thermal and dielectric properties of elastin and two soluble derivatives (κ-elastin and derived elastin peptides from enzymatic elastolysis) were investigated in the freeze-dried state in a wide temperature range (from -180 to +220°C). The glass transition of these amorphous proteins was studied by differential scanning calorimetry (DSC). The dielectric relaxations of both proteins were followed by thermally stimulated currents (TSC), an isochronal dielectric spectrometry running at variable temperature, analogous to a lowfrequency spectroscopy (10 -3 -10 -2 Hz) and by dynamic dielectric spectroscopy (DDS), performed isothermally with the frequency varying from 10 -2 to 3 × 10 6 Hz. The combination of TSC and DDS experiments and the determination of the activation parameters of the relaxation times inform about the molecular mobility of the proteins, both in the glassy state and in the liquid state. Major differences between the relaxation behavior of elastin and its soluble derivatives have been discussed and correlated with the molecular architecture of the proteins.
1999 Biochimie the struct elastin and functions
Elastin structures and their significance towards elastic recoil properties have been reviewed. Starting from the initial hypothesis that elastin conformation is conditioned by that of its monomer, the structure of tropoelastin was first described using theoretical and experimental methods and a [3 class folding type was evidenced for the isolated unbound tropoelastin molecules. The structure of elastin in the solid state was consistent with that of its monomer and consequently, fibrous elastin appeared constituted of globular tropoelastin molecules. Finally, theoretical and experimental considerations have led us to the conclusion that the functional form of the elastomer, water swollen elastin, could be a triphasic system comprising the protein chains, hydration water and solvent water. Following this description, the dynamic structural equilibria occurring within elastin hydrophobic domains and the plastisizing effect of water could explain elastin elasticity, in keeping with a classical entropic mechanism. © 1999 Soci6t6 frangaise de biochimie et biologie mol6culaire / Editions scientifiques et m6dicales Elsevier SAS elastin / secondary structures / elasticity
Molecular biophysics of elastin structure, function and pathology
Ciba Foundation symposium, 1995
Owing to the presence of the recurring sequence XPGX' (where X and X' are hydrophobic residues), the molecular structure of the sequences between cross-links in elastin is viewed primarily as a series of beta-turns which become helically ordered by hydrophobic folding into beta-spirals, which in turn assemble hydrophobically into twisted filaments. Both hydrophobic folding and assembly occur when the temperature is raised above Tt, the onset of an inverse temperature transition. Using poly[fv(VPGVG),fx(VPGXG)] (where fv and fx are mole fractions with fv + fx = 1 and X is now any of the naturally occurring amino acid residues), plots of fx versus Tt result in a new hydrophobicity scale based directly on the hydrophobic folding and assembly processes of interest. With the reference values chosen at fx = 1, the most hydrophobic residues of elastin, Tyr (Y) and Phe (F), have low values of Tt, -55 and -30 degrees C, respectively, and the most hydrophilic residues, Glu (E-), Asp (...
At a specific temperature, elastin-like polypeptides (ELPs) undergo a sharp solubility transition that can be exploited in a variety of applications in biotechnology and medicine. The temperature of the transition varies with ELP sequence, molecular weight, and concentration. We present a single equation of three parameters that quantitatively predicts the transition temperature as a function of ELP length and concentration for an ELP of a fixed composition. This model should be useful both for the design of new ELP sequences that exhibit a desired transition temperature and for the selection of variables to trigger the phase transition of an ELP for a given application.
Phase behavior and chain dynamics of elastin-like peptides versus amino acid sequences
Journal of Thermal Analysis and Calorimetry
Elastin fibrillogenesis is conditioned by multiple self-assembly processes. Previous studies have evidenced the crucial influence of amino acid specificities on molecular organization of glycine-rich elastin-like peptides, but also the important role of environment on the self-assembly processes. For the first time, we combined a differential scanning calorimetry (DSC) study on aqueous solutions of three elastin-like peptides with thermally stimulated currents (TSC) experiments in the condensed state. We have studied three pentadecapeptides having the XGGZG motif threefold repeated with X and Z residues constituted of valine and leucine, known to form fiber structures. Valine and leucine moieties differ only by the presence of-CH 2-spacer occupying in the pattern the first or the fourth position. Both of the residues are among the most abundant in elastin. Via DSC, we showed that the simple substitution of one amino acid strongly influences the surrounding hydration of the pentadecapeptides. During the self-assembly process, a slow exchange between bound water and bulk water is highlighted for (VGGLG) 3 , whereas a fast exchange of water molecules is found for (VGGVG) 3 and (LGGVG) 3. In the pre-fibrillar condensed state, TSC analysis reveals localized and delocalized motions and gives a fingerprint of the dynamics via activation parameters. At the localized level, a profound difference in the carbonyl environment is observed between (VGGLG) 3 and the other peptides. The delocalized chain dynamics of the three peptides can be connected to the different conformations. The dominant unordered conformation of (VGGLG) 3 leads to a softer system, while the large amount of b sheets and b turns in (VGGVG) 3 and (LGGVG) 3 leads to stiffer systems. Around the physiological temperature occurs a structural, isochronal phase transition, sequence specific, suggested to be associated with the ferroelectricity of such elastin-like peptides.
Water structure and elastin-like peptide aggregation
Journal of Thermal Analysis and Calorimetry, 2014
For the first time, calorimetric studies performed at very low temperature highlighted the preliminary and required conditions for further aggregation/coacervation of peptides from elastin in solution through the structural water reorganization around the peptides. For this purpose, we firstly characterized by turbidimetry and differential scanning calorimetry the synthetic S4 fragment peptide containing the XGGZG motif (where X and Z correspond to Valine or Leucine) which is able to form amyloid fibres under certain conditions. We also investigated two mediumsized elastin-related model elastin peptides containing the VGVPG motif (E50 and E18) as well as their analogues where proline is hydroxylated in hydroxyproline. These peptides were shown to coacervate, and a close correlation was found between the inverse transition temperature obtained by turbidimetry and the clathrate-like structures evidenced at low temperature by the calorimetric method.