Differential scanning calorimetry studies of NaCl effect on the inverse temperature transition of some elastin-based polytetra-, polypenta-, and polynonapeptides (original) (raw)
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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.
Journal of Molecular Biology, 1998
Elastin is a major protein component of the vascular wall and is responsible for its unusual elastic properties. Polymers of its repeating VPGVG sequences have been synthesised and shown to exhibit an inverse temperature transition where, as temperature rises, the polymer collapses from an extended chain to a b-spiral structure with three VPGVG units per turn, each pentamer adopting a type II b-turn conformation. These studies, however, have not established whether the temperature-driven conformational change is an intrinsic property of the individual pentameric sequences or a global, cooperative effect of many pentamers within the b-spiral structure. Here, we examine by circular dichroism the behaviour of elastin-like peptides (VPGVG) n , where n varies between 1 and 5. Remarkably, we ®nd that all lengths of peptide undergo an exten-ded23b-turn transition with increasing temperature, suggesting that the induction of the b-spiral occurs at the level of single pentameric units. The origin of this effect is a positive ÁS term for the transition. At 35 C, the average transition midpoint temperature, the value of TÁS is about 15 kcal mol À1. With larger oligomers (n 3), there is only a modest rise in ÁS, suggesting that the dominant entropic effect resides within the monomer and that interactions between these units make only a small contribution to the energetics of the transition. Charges at the termini, and residue replacements or additions, regulate the transitions for the short peptides in a manner similar to that observed for the longer polymers. The behaviour of the same peptides in tri¯uoroethanol and SDS solutions is consistent with formation of the b-turn being driven by interactions between non-polar groups. The signi®cance of this behaviour for the rational design of temperature-induced responses in proteins is discussed.
Sequential polypeptides. Part IX. The synthesis of two sequential polypeptide elastin models
International journal of peptide and protein research, 1975
We have recently reported (1) that the circular dichroism spectrum of the sequential polypentapeptide elastin model (I) in trifluoroethanol undergoes radical changes when small amounts of calcium ion are added. These changes are qualitatively similar to the effect of calcium ions on the circular dichroism spectra of some preparations obtained from natural elastin. Since the model (I) has no side-chain ligands this lends support to Urry's proposal (2) that the interaction of elastin with calcium ions involves co-ordination by backbone peptide groups rather than by sidechain functionalities. Urry has recently described (3) extensive experiments with synthetic oligo-and poly-peptides related to elastin. We now give details of the synthesis of our polypentapeptide and the related polytetrapeptide .
Journal of the American Chemical Society, 1981
Proton magnetic resonance and conformational energy calculations are presented for the cyclic peptide cycb(VPGVG), containing the pentamer repeat of elastin. The 'H NMR spectrum of the molecule is obtained in methanol and the temperature dependence of the peptide NH protons are reported for this solvent over the range 0-60 OC. The observation of a pentamer spectrum, at all temperatures, demonstrates that the molecule has a threefold symmetry on the 220-MHz time scale. ABX analysis is done for the Gly CH2 spin systems and the vicinal and *J geminal coupling constants are derived. From the observed coupling constants, acceptable ranges of values for the torsion angles, ,aboutN−C′bondsareworkedout.Reasonablerangesofvaluesfortorsionangles,, about N-C' bonds are worked out. Reasonable ranges of values for torsion angles, ,aboutN−C′bondsareworkedout.Reasonablerangesofvaluesfortorsionangles,, about the Ca-C bonds are gleaned from wire models built by using threefold symmetry and secondary structural constraints. By varying the backbone torsion angles within the ranges expected from coupling constants and from molecular models, it was possible to obtain a set of exactly threefold symmetric conformations. Conformational energy calculations are carried out, followed by detailed energy minimization. Six minimum energy structures are fully described. The torsion angles of three of these are consistent with NMR data. One of the structures is quite similar to the crystal structure of this molecule.
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.
Influence of the Amino-Acid Sequence on the Inverse Temperature Transition of Elastin-Like Polymers
Biophysical Journal, 2009
This work explores the dependence of the inverse temperature transition of elastin-like polymers (ELPs) on the amino-acid sequence, i.e., the amino-acid arrangement along the macromolecule and the resulting linear distribution of the physical properties (mainly polarity) derived from it. The hypothesis of this work is that, in addition to mean polarity and molecular mass, the given amino-acid sequence, or its equivalent-the way in which polarity is arranged along the molecule-is also relevant for determining the transition temperature and the latent heat of that transition. To test this hypothesis, a set of linear and di-and triblock ELP copolymers were designed and produced as recombinant proteins. The absolute sequence control provided by recombinant technologies allows the effect of the amino-acid arrangement to be isolated while keeping the molecular mass or mean polarity under strict control. The selected block copolymers were made of two different ELPs: one exhibiting temperature and pH responsiveness, and one exhibiting temperature responsiveness only. By changing the arrangement and length of the blocks while keeping other parameters, such as the molecular mass or mean polarity, constant, we were able to show that the sequence plays a key role in the smart behavior of ELPs.
Life
Elastin-like polypeptides (ELPs) are soluble in water at low temperature, but, on increasing the temperature, they undergo a reversible and cooperative, coil-to-globule collapse transition. It has been shown that the addition to water of either trimethylamine N-oxide (TMAO), glycine, or betaine causes a significant decrease of T(collapse) in the case of a specific ELP. Traditional rationalizations of these phenomena do not work in the present case. We show that an alternative approach, grounded in the magnitude of the solvent-excluded volume effect and its temperature dependence (strictly linked to the translational entropy of solvent and co-solute molecules), is able to rationalize the occurrence of ELP collapse in water on raising the temperature, as well as the T(collapse) lowering caused by the addition to water of either TMAO, glycine, or betaine.
International journal of peptide & protein research, 1981
The cyclopentapeptide, L.Val1-L.Pro2-Gly3-L.Val4-Gly5, was synthesized and its conformational characterization was carried out using n.m.r. and theoretical energy calculations. The n.m.r. studies indicated the existence of a cis Val1-Pro2 peptide bond in water and a very strong intramolecular H-bond between the val1 NH and Gly3 C=O groups. This H-bond forms a beta-turn (type II) placing Val4 and Gly5 residues within the turn. Two minimum energy conformations were derived, one of which agrees very well with the solution conformation.
Structure-activity relationships for some elastin-derived peptide chemoattractants
The Journal of Peptide Research, 2009
In an attempt to explore the relationships between conformation of chemotactic peptides related to elastin and their biological activity we have studied five peptides: VGVAPG, VGVPG, VGAPG, GVAPG and GGVPG in solvents of different polarities which may mimic the environmental conditions at the receptor site. CD and NMR studies showed that GVAPG has no preference for structured conformations, while the other peptides may assume folded conformations in organic solvents. All these peptides but GGVPG showed chemotactic activity for monocytes. The chemotactic activity of VGVPG, VGAPG and VGVAPG was inhibited by lactose, while chemotaxis of peptide GVAPG was insensitive to lactose, suggesting the existence of different chemotactic receptors. t 3 Munksgaard 1997.
High thermal stability and cold-denaturation of an artificial polypeptide
International Journal of Peptide and Protein Research, 2009
An amphipathic polypeptide, P,, with a tandemly repeated LKELPEKL sequence including a proline every eight residues, as well as a series of shorter peptides having the same sequence, P2, P3, P,, P, and P,, were synthesized. Their conformation in aqueous solution was mainly studied by CD. At low temperature, these peptides and polypeptide are completely unordered and undergo a reversible transition leading to a partly a-helical structure upon heating. Such behavior has been demonstrated for a few proteins by other authors and has been called cold-denaturation. The transition temperature of the polypeptide is close to 20 "C. The conformational change does not depend on concentration, indicating a monomolecular process. The high-temperature structure seems to be compact as for globular proteins. A model of folded structure is proposed from experimental data and from molecular modelling studies.