Hydrated elastin: Dynamics of water and protein followed by dielectric spectroscopies

The dielectric properties of elastin were investigated at different levels of hydration and specifically at the limit of freezable water apparition. The quantification of freezable water was performed by Differential Scanning Calorimetry (DSC). Two dielectric techniques were used to explore the dipolar relaxations of hydrated elastin: dynamic dielectric spectroscopy (DDS), performed isothermally with the frequency varying from 10(-2) to 3.10(-6) Hz, and the technique of thermally stimulated depolarization currents (TSDC), an isochronal spectrometry running at variable temperature, analogous to a low frequency spectroscopy {10(-3)– 10(-2) Hz}. A complex relaxation map was evidenced by the two techniques. Assignments for the different processes can be proposed by the combination of DDS and TSDC experiments and the determination of the activation parameters of the relaxation times. As already observed for globular proteins, the concept of "solvent-slaved" protein motions is checked for the fibrillar hydrated elastin

Changes in the physical structure and chain dynamics of elastin network in homocysteine-cultured arteries

The thermal and dielectric properties of the elastin network were investigated in arteries cultured with physiological and pathological concentrations of homocysteine, an aminoacid responsible of histological impairments in human arteries. The physical structure of this amorphous protein was investigated by differential scanning calorimetry (DSC). To explore the molecular dynamics of the elastin network in the nanometer range, we used thermally stimulated currents (TSC), a dielectric technique running at low frequency, and measuring the dipolar reorientations in proteins subjected to a static electrical field. Combining DSC and TSC experiments reveals the molecular mobility of the proteins, both in the glassy state and in the liquid state. Significant differences are evidenced in the physical structure and relaxation behavior of elastin network in cultured arteries (physiological and pathological concentrations of homocysteine) and discussed

Influence of homocysteine on the physical structure and molecular mobility of elastin network in cultured arteries

The thermal and dielectric properties of the elastin network were investigated in arteries cultured with physiological and pathological concentrations of homocysteine, an aminoacid responsible of histological impairments in human arteries. The glass transition of this amorphous protein was investigated by Differential Scanning Calorimetry (DSC). To explore the molecular dynamics of the elastin network in the nanometer range, we used Thermally Stimulated Currents (TSC), a dielectric technique running at low frequency and measuring the dipolar reorientations in proteins subjected to a static electrical field. Combining TSC and DSC experiments with determination of the activation parameters of relaxation times reveals the molecular mobility of the proteins. The major differences in the relaxation behavior of elastin between arteries cultured with physiological and pathological concentrations of homocysteine are discussed

Effect of Low-Temperature Plasma Jet on Thermal Stability and Physical Structure of Type I Collagen

This work is devoted to the characterization of type I collagen treated by a low-temperature plasma jet generated in ambient air to determine whether the resulting fibrous material is structurally preserved or reinforced. The physical structure of collagen is checked by differential scanning calorimetry (DSC), which is a well suited technique to analyze thermal transitions in proteins, such as denaturation. DSC is used to evaluate the thermal stability of collagen after the plasma treatments while Fourier transform infra red spectroscopy is used to check the integrity of triple helical domain and to investigate the effects of plasma treatments on the functional groups of collagen. It is more particularly shown that the plasma treatment can stabilize the collagen structure without altering the triple helical structure. This observation is supported by 1) the shift observed toward high-temperature range of the collagen denaturation and 2) the stiffening of the chains by a cross-linking action when compared to the control sample

Analysis of the molecular mobility of collagen and elastin in safe, atheromatous and aneurysmal aortas

Aim of the study : In this study, we propose to use a thermal technique, Differential Scanning Calorimetry (DSC) to follow the evolution of elastin and collagen in safe and pathological cardiovascular tissues. Patients and methods : The first part of this study deals with the analysis of the elastin network and associated proteins during ageing (from children to old persons) in aortic walls. The second part is devoted to the characterization of the collagenic phase in aneurysms. In both cases, physical data are correlated with biochemical analyses. Results and conclusion : For old persons aortas with atheromatous stades, elastin and associated proteins are found to interpenetrate to form a homogenous phase. Abdominal aortic aneurysms (AAA) are characterized by structural alterations of the aortic wall resulting from the degradation of elastic fibers and an increase of collagen/elastin ratio. Notable modifications are evidenced between collagen from control tissue and collagen from AAA, particularly concerning the thermal denaturation. Biochemical and thermal results are compatible with the increase of new collagen deposition and/or impairment of the collagen phase stability in the extracellular matrix of AAAs

Phase behavior and chain dynamics of elastin-like peptides versus amino acid sequences

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 –CH2– 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 phasetransition, sequence specific, suggested to be associated with the ferroelectricity of such elastin-like peptides

Influence of the architecture on the molecular mobility of synthetic fragments inspired from human tropoelastin

This work deals with the vibrational, thermal and dielectric characterization of a synthetic peptide (S4) released during the proteolysis of human tropoelastin. This peptide was shown to form amyloid-like fibers implied in neurodegenerative pathologies. The comparison between the linear peptides and the associated amyloidlike fibers evidences the strong influence of the secondary structures on the physical structure and chain dynamics of these polypeptides

Self-assembling peptide-enriched electrospun polycaprolactone scaffolds promote the h-osteoblast adhesion and modulate differentiation-associated gene expression

Electrospun polycaprolactone (PCL) is able to support the adhesion and growth of h-osteoblasts and to delay their degradation rate to a greater extent with respect to other polyesters. The drawbacks linked to its employment in regenerative medicine arise fromits hydrophobic nature and the lack of biochemical signals linked to it. This work reports on the attempt to add five different self-assembling (SA) peptides to PCL solutions before electrospinning. The hybrid scaffolds obtained had regular fibers (SEM analysis) whose diameters were similar to those of the extracellularmatrix, more stable hydrophilic (contact angle measurement) surfaces, and anamorphous phase constrained by peptides (DSC analysis). They appeared to have a notable capacity to promote the h-osteoblast adhesion and differentiation process by increasing the gene expression of alkaline phosphatase, bone sialoprotein, and osteopontin. Adding an Arg-Gly-Asp (RGD) motif to a self-assembling sequence was found to enhance cell adhesion, while the same motif condensed with a scrambled sequence did not, indicating that there is a cooperative effect between RGD and 3D architecture created by the self-assembling peptides. The study demonstrates that self-assembling peptide scaffolds are still able to promote beneficial effects on h-osteoblasts even after they have been included in electrospun polycaprolactone. The possibility of linking biochemical messages to self-assembling peptides could lead the way to a 3D decoration of fibrous scaffolds

Conformational and thermal characterization of a synthetic peptidic fragment inspired from human tropoelastin: Signature of the amyloid fibers

Objectives : This work deals with the conformational and thermal characterization of a synthetic peptide (S4) released during the proteolysis of human tropoelastin by the matrix metalloproteinase-12 that was shown to form amyloid-like fibres under certain conditions. Materials and methods : S4 peptides were synthesized by solid-phase methodology and aggregated in solution at 80 8C. Fourier transform–infrared spectroscopy (FT–IR) was used to access the secondary structure. Thermal characterization was performed by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Results : The DSC study of the soluble linear peptide S4 in solution in TBS reveals the irreversible aggregation into amyloid fibres. FT–IR, DSC and TGA analyses performed on freeze-dried samples evidence differences between the linear peptide and its associated amyloid-like fibres, both on the conformation and the physical structure. When S4 peptides are aggregated, the prominent conformation scanned by FT–IR is the cross b-structure, corresponding to TGA to an increase of the thermal stability. Moreover, the DSC thermograms of S4 fibres are characteristic of a highly ordered structure, in contrast to the DSC thermograms of S4 linear peptides, characteristic of an amorphous structure. Finally, the DSC analysis of differently hydrated S4 fibres brings to the fore the specific thermal answer of the wet interfaces of the cross b-fibres. Conclusion : FT–IR and thermal techniques are well suited to evidence conformational and structural differences between the soluble peptide and its amyloid form

Dielectric relaxations and ferroelectric behaviour of even–odd polyamide PA 6,9

Thermo Stimulated Current (TSC) combined with Dynamic Dielectric Spectroscopy (DDS) have been applied to the investigation of dielectric relaxation modes of an even–odd Polyamide PA 6,9. The correlation between results obtained by both methods allows us to describe precisely the molecular mobility. At high temperature, the various dielectric relaxation phenomena are separated by applying the dielectric modulus formalism. The comparison between the activation enthalpy values obtained by DDS and TSC leads to the assignment of the so-called α mode to cooperative movements of polymeric sequences. Molecular mobility of PA 6,9 is compared with the one of PA 11. The piezoelectric activity of PA 6,9 is shown and analyzed