Circular dichroism measurements on aqueous solutions of alpha-elastin have given evidence of beta... more Circular dichroism measurements on aqueous solutions of alpha-elastin have given evidence of beta-bend structure at elevated concentrations. When Ca2+ was added, the concentration-dependent conformational transition was somewhat inhibited and the binding of the metal ion was shown, by means of equilibrium dialysis, to be essentially independent from alpha-elastin concentration in the range of 1 to 10 mg/ml. The results obtained are discussed in connection with the elasticity and calcification of elastin.
Proceedings. Biological sciences / The Royal Society, Jan 22, 1995
Recent results with the Drosophila melanogaster period gene suggest that the apparently conserved... more Recent results with the Drosophila melanogaster period gene suggest that the apparently conserved repetitive motif (Thr-Gly)n encoded by this gene may play an important role in the temperature compensation of the circadian clock. We have therefore initiated both a theoretical and experimental conformational analysis of (Thr-Gly)n peptides. By using a build-up method, it is clear that the hexapeptide (Thr-Gly)3 represents a 'conformational monomer' and generates a stable type II or type III beta-turn. Circular dichroism and nuclear magnetic resonance spectra of synthetic (Thr-Gly)3 and poly(Thr-Gly) peptides revealed that these peptides exhibit flexible conformations, especially in more polar environments and at higher temperatures. We speculate that this flexibility may illuminate our understanding of both the molecular mechanism of temperature compensation and the systematic geographical distribution within Europe of the Thr-Gly length polymorphism in D. melanogaster.
International journal of peptide and protein research, 1984
The synthetic polytripeptides poly(Gly-Pro-Ile) and poly(Gly-Ile-Pro) were studied both experimen... more The synthetic polytripeptides poly(Gly-Pro-Ile) and poly(Gly-Ile-Pro) were studied both experimentally (mainly by circular dichroism spectroscopy) and theoretically by quantum mechanical methods. Poly(Gly-Ile-Pro) adopts a collagen-like structure under favourable conditions while the isomeric poly(Gly-Pro-Ile) does not. Theoretical studies emphasize severe intrastrand interactions which limit the main chain conformations in the case of poly(Gly-Ile-Pro). On the other hand, both the side cahin and the backbone in poly(Gly-Pro-Ile) can take up many different local conformations. Therefore, it seems that the conformational behaviour of synthetic polytripeptides can be at least partially explained in terms of local interactions.
International Journal of Peptide and Protein Research, 1987
The title polytripeptides were synthesized and studied experimentally, by circular dichroism, and... more The title polytripeptides were synthesized and studied experimentally, by circular dichroism, and theoretically, by quantum mechanical methods. With the exception of poly(Gly-Pro-Val), which was found to be essentially structureless in solution, the other polymers adopt folded conformations, most probably of type II beta-bends. Conclusions from theoretical studies were generally in agreement with the experimental results. In particular, it is noteworthy that the optimized (phi, psi) maps for poly(Gly-Pro-Met) showed the absolute minimum (phi = 60 degree, psi = 0 degrees) located inside the beta II bend space.
In this paper, we report the characterization of copper(II) complexes with two prion (PrP) protei... more In this paper, we report the characterization of copper(II) complexes with two prion (PrP) protein peptide fragment analogues (VNITKQHTVTTTT), one with the N-terminus acetylated and the C-terminus amidated (PrP Ac180-193NH2) and the other with both the C- and N-termini free (PrP 180-193). Such peptide sequence almost entirely encompasses the PrPC's helix 2 in the C-terminal region. The stoichiometry, the binding modes and the conformational features of the copper(II) complexes with the above mentioned two peptides were investigated by electrospray ionization-mass spectrometry (ESI-MS), UV-visible (UV-Vis) spectrometry and electron paramagnetic resonance (EPR) spectrometry as well as by circular dichroism (CD) measurements. The binding site location of copper(II) in the structured region of the protein can be here suggested on the basis of our findings that show the involvement of His 187 residue. The similarity of the EPR parameters suggests that the anchoring imidazole residue drives the copper(II) coordination environment towards a common binding motif in different regions of the prion protein.
Journal of Biomolecular Structure and Dynamics, 1992
Poly (Val-Gly-Gly-Leu-Gly), a polypeptide mimicking the physico-chemical properties of the glycin... more Poly (Val-Gly-Gly-Leu-Gly), a polypeptide mimicking the physico-chemical properties of the glycine-rich regions of elastin, has been synthesized and studied both in solution and in the aggregated state. By comparison, also the conformation of different "monomeric" units has been investigated. The polymer showed increased disorder with respect to the "monomers", the molecular conformation being accounted for by a more or less random collection of isolated beta-turns. Nevertheless, in the solid state the polymer is able to adopt supramolecular structures reminiscent of those found for elastin.
International Journal of Biological Macromolecules, 1992
Differential scanning calorimetry (d.s.c.) and thermally stimulated current (t.s.c.) have been ap... more Differential scanning calorimetry (d.s.c.) and thermally stimulated current (t.s.c.) have been applied to the study of thermal transitions and dielectric relaxations of a pentapeptide sequence: Gly-Leu-Gly-Gly-Val of elastin. The manifestation of the glass transition has been observed by both techniques. The analysis of the fine structure of t.s.c. spectra reveals the existence of local order in the amorphous phase upon physical ageing. In the 'true' amorphous phase, cooperative motions of sequences of various length are observed. The corresponding activation parameters are characteristic of the 'structure' of the amorphous phase and might be used as reference for further studies.
International Journal of Biological Macromolecules, 1982
ABSTRACT Circular dichroism measurements on methionyl-containing diketopiperazines have shown tha... more ABSTRACT Circular dichroism measurements on methionyl-containing diketopiperazines have shown that the thioether side chain favours the appearance of fold conformations in the ring. A solvent-dependent conformational distribution has been also found in the case of l-methionylglycine diketopiperazzine.
International Journal of Biological Macromolecules, 1990
Spectroscopic studies on synthetic polypeptides containing the unit-X-G-G (X=V or L) are reported... more Spectroscopic studies on synthetic polypeptides containing the unit-X-G-G (X=V or L) are reported. The sequences, constituting either fragments or model of elastin, were shown to adopt type II beta-turns together with an ensemble of unordered conformations. Furthermore, it was found that the stability of the beta-turns was depending on the nature of the X residue, on the hydration of the chain and, in the case of the sequence G-V-G-G-L, was decreasing by increasing the length of the chain.
International Journal of Biological Macromolecules, 1982
ABSTRACT α-Elastins from young and old human aortas have been prepared and the interaction of the... more ABSTRACT α-Elastins from young and old human aortas have been prepared and the interaction of these modified proteins with taurocholate, oleate, linoleate and palmitoleate has been studied by means of circular dichroism. Multiple conformational transitions were observed possibly involving, in addition to the aperiodic form, structures such as the β-bend and β-like forms. At the molecular level, a correlation between the aging of elastin and its interaction with lipids has been found that could be extended, at the macroscopic scale, to processes such as atherosclerosis and aging of the arterial wall.
Circular dichroism measurements on aqueous solutions of alpha-elastin have given evidence of beta... more Circular dichroism measurements on aqueous solutions of alpha-elastin have given evidence of beta-bend structure at elevated concentrations. When Ca2+ was added, the concentration-dependent conformational transition was somewhat inhibited and the binding of the metal ion was shown, by means of equilibrium dialysis, to be essentially independent from alpha-elastin concentration in the range of 1 to 10 mg/ml. The results obtained are discussed in connection with the elasticity and calcification of elastin.
Proceedings. Biological sciences / The Royal Society, Jan 22, 1995
Recent results with the Drosophila melanogaster period gene suggest that the apparently conserved... more Recent results with the Drosophila melanogaster period gene suggest that the apparently conserved repetitive motif (Thr-Gly)n encoded by this gene may play an important role in the temperature compensation of the circadian clock. We have therefore initiated both a theoretical and experimental conformational analysis of (Thr-Gly)n peptides. By using a build-up method, it is clear that the hexapeptide (Thr-Gly)3 represents a 'conformational monomer' and generates a stable type II or type III beta-turn. Circular dichroism and nuclear magnetic resonance spectra of synthetic (Thr-Gly)3 and poly(Thr-Gly) peptides revealed that these peptides exhibit flexible conformations, especially in more polar environments and at higher temperatures. We speculate that this flexibility may illuminate our understanding of both the molecular mechanism of temperature compensation and the systematic geographical distribution within Europe of the Thr-Gly length polymorphism in D. melanogaster.
International journal of peptide and protein research, 1984
The synthetic polytripeptides poly(Gly-Pro-Ile) and poly(Gly-Ile-Pro) were studied both experimen... more The synthetic polytripeptides poly(Gly-Pro-Ile) and poly(Gly-Ile-Pro) were studied both experimentally (mainly by circular dichroism spectroscopy) and theoretically by quantum mechanical methods. Poly(Gly-Ile-Pro) adopts a collagen-like structure under favourable conditions while the isomeric poly(Gly-Pro-Ile) does not. Theoretical studies emphasize severe intrastrand interactions which limit the main chain conformations in the case of poly(Gly-Ile-Pro). On the other hand, both the side cahin and the backbone in poly(Gly-Pro-Ile) can take up many different local conformations. Therefore, it seems that the conformational behaviour of synthetic polytripeptides can be at least partially explained in terms of local interactions.
International Journal of Peptide and Protein Research, 1987
The title polytripeptides were synthesized and studied experimentally, by circular dichroism, and... more The title polytripeptides were synthesized and studied experimentally, by circular dichroism, and theoretically, by quantum mechanical methods. With the exception of poly(Gly-Pro-Val), which was found to be essentially structureless in solution, the other polymers adopt folded conformations, most probably of type II beta-bends. Conclusions from theoretical studies were generally in agreement with the experimental results. In particular, it is noteworthy that the optimized (phi, psi) maps for poly(Gly-Pro-Met) showed the absolute minimum (phi = 60 degree, psi = 0 degrees) located inside the beta II bend space.
In this paper, we report the characterization of copper(II) complexes with two prion (PrP) protei... more In this paper, we report the characterization of copper(II) complexes with two prion (PrP) protein peptide fragment analogues (VNITKQHTVTTTT), one with the N-terminus acetylated and the C-terminus amidated (PrP Ac180-193NH2) and the other with both the C- and N-termini free (PrP 180-193). Such peptide sequence almost entirely encompasses the PrPC's helix 2 in the C-terminal region. The stoichiometry, the binding modes and the conformational features of the copper(II) complexes with the above mentioned two peptides were investigated by electrospray ionization-mass spectrometry (ESI-MS), UV-visible (UV-Vis) spectrometry and electron paramagnetic resonance (EPR) spectrometry as well as by circular dichroism (CD) measurements. The binding site location of copper(II) in the structured region of the protein can be here suggested on the basis of our findings that show the involvement of His 187 residue. The similarity of the EPR parameters suggests that the anchoring imidazole residue drives the copper(II) coordination environment towards a common binding motif in different regions of the prion protein.
Journal of Biomolecular Structure and Dynamics, 1992
Poly (Val-Gly-Gly-Leu-Gly), a polypeptide mimicking the physico-chemical properties of the glycin... more Poly (Val-Gly-Gly-Leu-Gly), a polypeptide mimicking the physico-chemical properties of the glycine-rich regions of elastin, has been synthesized and studied both in solution and in the aggregated state. By comparison, also the conformation of different "monomeric" units has been investigated. The polymer showed increased disorder with respect to the "monomers", the molecular conformation being accounted for by a more or less random collection of isolated beta-turns. Nevertheless, in the solid state the polymer is able to adopt supramolecular structures reminiscent of those found for elastin.
International Journal of Biological Macromolecules, 1992
Differential scanning calorimetry (d.s.c.) and thermally stimulated current (t.s.c.) have been ap... more Differential scanning calorimetry (d.s.c.) and thermally stimulated current (t.s.c.) have been applied to the study of thermal transitions and dielectric relaxations of a pentapeptide sequence: Gly-Leu-Gly-Gly-Val of elastin. The manifestation of the glass transition has been observed by both techniques. The analysis of the fine structure of t.s.c. spectra reveals the existence of local order in the amorphous phase upon physical ageing. In the 'true' amorphous phase, cooperative motions of sequences of various length are observed. The corresponding activation parameters are characteristic of the 'structure' of the amorphous phase and might be used as reference for further studies.
International Journal of Biological Macromolecules, 1982
ABSTRACT Circular dichroism measurements on methionyl-containing diketopiperazines have shown tha... more ABSTRACT Circular dichroism measurements on methionyl-containing diketopiperazines have shown that the thioether side chain favours the appearance of fold conformations in the ring. A solvent-dependent conformational distribution has been also found in the case of l-methionylglycine diketopiperazzine.
International Journal of Biological Macromolecules, 1990
Spectroscopic studies on synthetic polypeptides containing the unit-X-G-G (X=V or L) are reported... more Spectroscopic studies on synthetic polypeptides containing the unit-X-G-G (X=V or L) are reported. The sequences, constituting either fragments or model of elastin, were shown to adopt type II beta-turns together with an ensemble of unordered conformations. Furthermore, it was found that the stability of the beta-turns was depending on the nature of the X residue, on the hydration of the chain and, in the case of the sequence G-V-G-G-L, was decreasing by increasing the length of the chain.
International Journal of Biological Macromolecules, 1982
ABSTRACT α-Elastins from young and old human aortas have been prepared and the interaction of the... more ABSTRACT α-Elastins from young and old human aortas have been prepared and the interaction of these modified proteins with taurocholate, oleate, linoleate and palmitoleate has been studied by means of circular dichroism. Multiple conformational transitions were observed possibly involving, in addition to the aperiodic form, structures such as the β-bend and β-like forms. At the molecular level, a correlation between the aging of elastin and its interaction with lipids has been found that could be extended, at the macroscopic scale, to processes such as atherosclerosis and aging of the arterial wall.
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