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Claudio Toniolo - One of the best experts on this subject based on the ideXlab platform.

  • Looking for the peptide 2.05‐Helix: A solvent‐ and main‐chain length‐dependent conformational switch probed by electron transfer across cα,α‐diethylglycine homo‐oligomers
    Biopolymers, 2013
    Co-Authors: Raffaella Lettieri, Claudio Toniolo, Marco Crisma, Fernando Formaggio, Martina Bischetti, Emanuela Gatto, Antonio Palleschi, Elisabetta Ricci, Mariano Venanzi
    Abstract:

    The elusive, multiple fully extended (2.05-Helix) peptide conformation was searched with a series of Cα,α-diethylglycine homo-oligomers (n = 1 to 5) functionalized by an electron transfer (ET) donor···acceptor (D···A) pair in acetonitrile and chloroform solutions. In the former solvent, all peptides investigated were shown to populate the 310-Helix conformation, whereas in chloroform the two shortest members of the series (n = 1 and n = 2) adopt predominantly the 2.05-Helix. Interestingly, for the longest components (n = 3 to n = 5) in this latter solvent, an equilibrium between the 2.05- and 310-helices takes place, the latter conformation becoming progressively more populated as the peptide main-chain length increases. Time-resolved fluorescence (TRF) experiments and molecular mechanics (MM) calculations were used in a combined approach to analyze the ET efficiencies and to associate a specific conformer (from MM) to an experimentally determined ET rate constant (from TRF). Therefore, because of the high sensitivity of the ET process to the D···A distance, ET can be used as a kinetic spectroscopic ruler, allowing for the characterization of the transition from a pure 310-Helix conformation to a 2.05-/310-Helix equilibrium for the longest Deg homo-peptides of this series upon changing the solvent from acetonitrile to chloroform. To our knowledge, this is the first time that the electronic coupling factor β for ET across a peptide chain in the 2.05-Helix conformation is provided. © 2012 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 100: 51–63, 2013.

  • first homo peptides undergoing a reversible 310 Helix α Helix transition critical main chain length
    Biopolymers, 2008
    Co-Authors: Alessandro Moretto, Fernando Formaggio, Quirinus B Broxterman, Bernard Kaptein, Timothy A Keiderling, Ling Wu, Claudio Toniolo
    Abstract:

    The difference in length between the more elongated peptide 310-Helix and the more compact α-Helix is about 0.4 A/residue. This property makes the 310-/α-Helix reversible conversion very promising as a molecular switching tool between the N- and C-terminal functions of a peptide backbone. In this work, using homo-peptides of various main-chain length, all based on the strongly helicogenic, Cα-tetrasubstituted α-amino acid Cα-methyl-L-valine, we show that a well defined, solvent controlled, reversible 310-/α-Helix transition takes place even in a homo-oligomer as short as a terminally blocked hexapeptide. Homo-peptide sequences blocked as a urethane or an acetamide at the N-terminus and as a methyl ester or an N-alkyl amide at the C-terminus are all appropriate. The nature of the occurring helical species in the various solvents tested was assessed by electronic or vibrational circular dichroism. © 2008 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 90: 567–574, 2008. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com

  • First homo‐peptides undergoing a reversible 310‐Helix/α‐Helix transition: Critical main‐chain length
    Biopolymers, 2008
    Co-Authors: Alessandro Moretto, Fernando Formaggio, Quirinus B Broxterman, Bernard Kaptein, Timothy A Keiderling, Ling Wu, Claudio Toniolo
    Abstract:

    The difference in length between the more elongated peptide 310-Helix and the more compact α-Helix is about 0.4 A/residue. This property makes the 310-/α-Helix reversible conversion very promising as a molecular switching tool between the N- and C-terminal functions of a peptide backbone. In this work, using homo-peptides of various main-chain length, all based on the strongly helicogenic, Cα-tetrasubstituted α-amino acid Cα-methyl-L-valine, we show that a well defined, solvent controlled, reversible 310-/α-Helix transition takes place even in a homo-oligomer as short as a terminally blocked hexapeptide. Homo-peptide sequences blocked as a urethane or an acetamide at the N-terminus and as a methyl ester or an N-alkyl amide at the C-terminus are all appropriate. The nature of the occurring helical species in the various solvents tested was assessed by electronic or vibrational circular dichroism. © 2008 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 90: 567–574, 2008. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com

  • Peptide α/310-Helix Dimorphism in the Crystal State
    Journal of the American Chemical Society, 2007
    Co-Authors: Marco Crisma, Michele Saviano, Alessandro Moretto, Quirinus B Broxterman, Bernard Kaptein, Claudio Toniolo
    Abstract:

    The fully Cα-methylated homo-peptide Ac-[l-(αMe)Val]7-NHiPr is completely 310-helical when its crystals are grown from a methanol solution, whereas it is α-helical when crystallized from HFIP (1,1,1,3,3,3-hexafluoropropan-2-ol), thus providing an example of a solvent-driven α/310-Helix dimorphism in the crystal state. The interactions of cocrystallized HFIP molecules with the peptide in the α-helical structure are reported.

  • peptide α 310 Helix dimorphism in the crystal state
    Journal of the American Chemical Society, 2007
    Co-Authors: Marco Crisma, Michele Saviano, Alessandro Moretto, Quirinus B Broxterman, Bernard Kaptein, Claudio Toniolo
    Abstract:

    The fully Cα-methylated homo-peptide Ac-[l-(αMe)Val]7-NHiPr is completely 310-helical when its crystals are grown from a methanol solution, whereas it is α-helical when crystallized from HFIP (1,1,1,3,3,3-hexafluoropropan-2-ol), thus providing an example of a solvent-driven α/310-Helix dimorphism in the crystal state. The interactions of cocrystallized HFIP molecules with the peptide in the α-helical structure are reported.

Fernando Formaggio - One of the best experts on this subject based on the ideXlab platform.

  • Looking for the peptide 2.05‐Helix: A solvent‐ and main‐chain length‐dependent conformational switch probed by electron transfer across cα,α‐diethylglycine homo‐oligomers
    Biopolymers, 2013
    Co-Authors: Raffaella Lettieri, Claudio Toniolo, Marco Crisma, Fernando Formaggio, Martina Bischetti, Emanuela Gatto, Antonio Palleschi, Elisabetta Ricci, Mariano Venanzi
    Abstract:

    The elusive, multiple fully extended (2.05-Helix) peptide conformation was searched with a series of Cα,α-diethylglycine homo-oligomers (n = 1 to 5) functionalized by an electron transfer (ET) donor···acceptor (D···A) pair in acetonitrile and chloroform solutions. In the former solvent, all peptides investigated were shown to populate the 310-Helix conformation, whereas in chloroform the two shortest members of the series (n = 1 and n = 2) adopt predominantly the 2.05-Helix. Interestingly, for the longest components (n = 3 to n = 5) in this latter solvent, an equilibrium between the 2.05- and 310-helices takes place, the latter conformation becoming progressively more populated as the peptide main-chain length increases. Time-resolved fluorescence (TRF) experiments and molecular mechanics (MM) calculations were used in a combined approach to analyze the ET efficiencies and to associate a specific conformer (from MM) to an experimentally determined ET rate constant (from TRF). Therefore, because of the high sensitivity of the ET process to the D···A distance, ET can be used as a kinetic spectroscopic ruler, allowing for the characterization of the transition from a pure 310-Helix conformation to a 2.05-/310-Helix equilibrium for the longest Deg homo-peptides of this series upon changing the solvent from acetonitrile to chloroform. To our knowledge, this is the first time that the electronic coupling factor β for ET across a peptide chain in the 2.05-Helix conformation is provided. © 2012 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 100: 51–63, 2013.

  • First homo‐peptides undergoing a reversible 310‐Helix/α‐Helix transition: Critical main‐chain length
    Biopolymers, 2008
    Co-Authors: Alessandro Moretto, Fernando Formaggio, Quirinus B Broxterman, Bernard Kaptein, Timothy A Keiderling, Ling Wu, Claudio Toniolo
    Abstract:

    The difference in length between the more elongated peptide 310-Helix and the more compact α-Helix is about 0.4 A/residue. This property makes the 310-/α-Helix reversible conversion very promising as a molecular switching tool between the N- and C-terminal functions of a peptide backbone. In this work, using homo-peptides of various main-chain length, all based on the strongly helicogenic, Cα-tetrasubstituted α-amino acid Cα-methyl-L-valine, we show that a well defined, solvent controlled, reversible 310-/α-Helix transition takes place even in a homo-oligomer as short as a terminally blocked hexapeptide. Homo-peptide sequences blocked as a urethane or an acetamide at the N-terminus and as a methyl ester or an N-alkyl amide at the C-terminus are all appropriate. The nature of the occurring helical species in the various solvents tested was assessed by electronic or vibrational circular dichroism. © 2008 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 90: 567–574, 2008. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com

  • first homo peptides undergoing a reversible 310 Helix α Helix transition critical main chain length
    Biopolymers, 2008
    Co-Authors: Alessandro Moretto, Fernando Formaggio, Quirinus B Broxterman, Bernard Kaptein, Timothy A Keiderling, Ling Wu, Claudio Toniolo
    Abstract:

    The difference in length between the more elongated peptide 310-Helix and the more compact α-Helix is about 0.4 A/residue. This property makes the 310-/α-Helix reversible conversion very promising as a molecular switching tool between the N- and C-terminal functions of a peptide backbone. In this work, using homo-peptides of various main-chain length, all based on the strongly helicogenic, Cα-tetrasubstituted α-amino acid Cα-methyl-L-valine, we show that a well defined, solvent controlled, reversible 310-/α-Helix transition takes place even in a homo-oligomer as short as a terminally blocked hexapeptide. Homo-peptide sequences blocked as a urethane or an acetamide at the N-terminus and as a methyl ester or an N-alkyl amide at the C-terminus are all appropriate. The nature of the occurring helical species in the various solvents tested was assessed by electronic or vibrational circular dichroism. © 2008 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 90: 567–574, 2008. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com

  • Slow tert‐butyl ester acidolysis and peptide 310‐Helix to α‐Helix transition in HFIP solution
    Biopolymers, 2007
    Co-Authors: Alessandro Moretto, Marco Crisma, Fernando Formaggio, Quirinus B Broxterman, Bernard Kaptein, Timothy A Keiderling, Claudio Toniolo
    Abstract:

    We have already shown by CD and NMR techniques that the terminally protected homo-octapeptides Z (and Ac)-[L-(αMe)Val]8-OtBu undergo a slow and irreversible 310-Helix to α-Helix transition when dissolved in 1,1,1,3,3,3-hexafluoroisopropanol. In the present work, we find by HPLC and CD that under the aforementioned experimental conditions, a slow acidolysis of the tert-butyl ester functionality does take place affording the corresponding octapeptide free acids. The results of our combined chromatographic and spectroscopic experiments are confirmed by a comparison with the properties of independently synthesized and chemically characterized authentic compounds. © 2007 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 88: 233–238, 2007. This article was originally published online as an accepted preprint. The ‘Published Online’ date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com

  • slow tert butyl ester acidolysis and peptide 310 Helix to α Helix transition in hfip solution
    Biopolymers, 2007
    Co-Authors: Alessandro Moretto, Marco Crisma, Fernando Formaggio, Quirinus B Broxterman, Bernard Kaptein, Timothy A Keiderling, Claudio Toniolo
    Abstract:

    We have already shown by CD and NMR techniques that the terminally protected homo-octapeptides Z (and Ac)-[L-(αMe)Val]8-OtBu undergo a slow and irreversible 310-Helix to α-Helix transition when dissolved in 1,1,1,3,3,3-hexafluoroisopropanol. In the present work, we find by HPLC and CD that under the aforementioned experimental conditions, a slow acidolysis of the tert-butyl ester functionality does take place affording the corresponding octapeptide free acids. The results of our combined chromatographic and spectroscopic experiments are confirmed by a comparison with the properties of independently synthesized and chemically characterized authentic compounds. © 2007 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 88: 233–238, 2007. This article was originally published online as an accepted preprint. The ‘Published Online’ date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com

Marco Crisma - One of the best experts on this subject based on the ideXlab platform.

  • Looking for the peptide 2.05‐Helix: A solvent‐ and main‐chain length‐dependent conformational switch probed by electron transfer across cα,α‐diethylglycine homo‐oligomers
    Biopolymers, 2013
    Co-Authors: Raffaella Lettieri, Claudio Toniolo, Marco Crisma, Fernando Formaggio, Martina Bischetti, Emanuela Gatto, Antonio Palleschi, Elisabetta Ricci, Mariano Venanzi
    Abstract:

    The elusive, multiple fully extended (2.05-Helix) peptide conformation was searched with a series of Cα,α-diethylglycine homo-oligomers (n = 1 to 5) functionalized by an electron transfer (ET) donor···acceptor (D···A) pair in acetonitrile and chloroform solutions. In the former solvent, all peptides investigated were shown to populate the 310-Helix conformation, whereas in chloroform the two shortest members of the series (n = 1 and n = 2) adopt predominantly the 2.05-Helix. Interestingly, for the longest components (n = 3 to n = 5) in this latter solvent, an equilibrium between the 2.05- and 310-helices takes place, the latter conformation becoming progressively more populated as the peptide main-chain length increases. Time-resolved fluorescence (TRF) experiments and molecular mechanics (MM) calculations were used in a combined approach to analyze the ET efficiencies and to associate a specific conformer (from MM) to an experimentally determined ET rate constant (from TRF). Therefore, because of the high sensitivity of the ET process to the D···A distance, ET can be used as a kinetic spectroscopic ruler, allowing for the characterization of the transition from a pure 310-Helix conformation to a 2.05-/310-Helix equilibrium for the longest Deg homo-peptides of this series upon changing the solvent from acetonitrile to chloroform. To our knowledge, this is the first time that the electronic coupling factor β for ET across a peptide chain in the 2.05-Helix conformation is provided. © 2012 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 100: 51–63, 2013.

  • peptide α 310 Helix dimorphism in the crystal state
    Journal of the American Chemical Society, 2007
    Co-Authors: Marco Crisma, Michele Saviano, Alessandro Moretto, Quirinus B Broxterman, Bernard Kaptein, Claudio Toniolo
    Abstract:

    The fully Cα-methylated homo-peptide Ac-[l-(αMe)Val]7-NHiPr is completely 310-helical when its crystals are grown from a methanol solution, whereas it is α-helical when crystallized from HFIP (1,1,1,3,3,3-hexafluoropropan-2-ol), thus providing an example of a solvent-driven α/310-Helix dimorphism in the crystal state. The interactions of cocrystallized HFIP molecules with the peptide in the α-helical structure are reported.

  • Peptide α/310-Helix Dimorphism in the Crystal State
    Journal of the American Chemical Society, 2007
    Co-Authors: Marco Crisma, Michele Saviano, Alessandro Moretto, Quirinus B Broxterman, Bernard Kaptein, Claudio Toniolo
    Abstract:

    The fully Cα-methylated homo-peptide Ac-[l-(αMe)Val]7-NHiPr is completely 310-helical when its crystals are grown from a methanol solution, whereas it is α-helical when crystallized from HFIP (1,1,1,3,3,3-hexafluoropropan-2-ol), thus providing an example of a solvent-driven α/310-Helix dimorphism in the crystal state. The interactions of cocrystallized HFIP molecules with the peptide in the α-helical structure are reported.

  • slow tert butyl ester acidolysis and peptide 310 Helix to α Helix transition in hfip solution
    Biopolymers, 2007
    Co-Authors: Alessandro Moretto, Marco Crisma, Fernando Formaggio, Quirinus B Broxterman, Bernard Kaptein, Timothy A Keiderling, Claudio Toniolo
    Abstract:

    We have already shown by CD and NMR techniques that the terminally protected homo-octapeptides Z (and Ac)-[L-(αMe)Val]8-OtBu undergo a slow and irreversible 310-Helix to α-Helix transition when dissolved in 1,1,1,3,3,3-hexafluoroisopropanol. In the present work, we find by HPLC and CD that under the aforementioned experimental conditions, a slow acidolysis of the tert-butyl ester functionality does take place affording the corresponding octapeptide free acids. The results of our combined chromatographic and spectroscopic experiments are confirmed by a comparison with the properties of independently synthesized and chemically characterized authentic compounds. © 2007 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 88: 233–238, 2007. This article was originally published online as an accepted preprint. The ‘Published Online’ date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com

  • Slow tert‐butyl ester acidolysis and peptide 310‐Helix to α‐Helix transition in HFIP solution
    Biopolymers, 2007
    Co-Authors: Alessandro Moretto, Marco Crisma, Fernando Formaggio, Quirinus B Broxterman, Bernard Kaptein, Timothy A Keiderling, Claudio Toniolo
    Abstract:

    We have already shown by CD and NMR techniques that the terminally protected homo-octapeptides Z (and Ac)-[L-(αMe)Val]8-OtBu undergo a slow and irreversible 310-Helix to α-Helix transition when dissolved in 1,1,1,3,3,3-hexafluoroisopropanol. In the present work, we find by HPLC and CD that under the aforementioned experimental conditions, a slow acidolysis of the tert-butyl ester functionality does take place affording the corresponding octapeptide free acids. The results of our combined chromatographic and spectroscopic experiments are confirmed by a comparison with the properties of independently synthesized and chemically characterized authentic compounds. © 2007 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 88: 233–238, 2007. This article was originally published online as an accepted preprint. The ‘Published Online’ date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com

Quirinus B Broxterman - One of the best experts on this subject based on the ideXlab platform.

  • first homo peptides undergoing a reversible 310 Helix α Helix transition critical main chain length
    Biopolymers, 2008
    Co-Authors: Alessandro Moretto, Fernando Formaggio, Quirinus B Broxterman, Bernard Kaptein, Timothy A Keiderling, Ling Wu, Claudio Toniolo
    Abstract:

    The difference in length between the more elongated peptide 310-Helix and the more compact α-Helix is about 0.4 A/residue. This property makes the 310-/α-Helix reversible conversion very promising as a molecular switching tool between the N- and C-terminal functions of a peptide backbone. In this work, using homo-peptides of various main-chain length, all based on the strongly helicogenic, Cα-tetrasubstituted α-amino acid Cα-methyl-L-valine, we show that a well defined, solvent controlled, reversible 310-/α-Helix transition takes place even in a homo-oligomer as short as a terminally blocked hexapeptide. Homo-peptide sequences blocked as a urethane or an acetamide at the N-terminus and as a methyl ester or an N-alkyl amide at the C-terminus are all appropriate. The nature of the occurring helical species in the various solvents tested was assessed by electronic or vibrational circular dichroism. © 2008 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 90: 567–574, 2008. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com

  • First homo‐peptides undergoing a reversible 310‐Helix/α‐Helix transition: Critical main‐chain length
    Biopolymers, 2008
    Co-Authors: Alessandro Moretto, Fernando Formaggio, Quirinus B Broxterman, Bernard Kaptein, Timothy A Keiderling, Ling Wu, Claudio Toniolo
    Abstract:

    The difference in length between the more elongated peptide 310-Helix and the more compact α-Helix is about 0.4 A/residue. This property makes the 310-/α-Helix reversible conversion very promising as a molecular switching tool between the N- and C-terminal functions of a peptide backbone. In this work, using homo-peptides of various main-chain length, all based on the strongly helicogenic, Cα-tetrasubstituted α-amino acid Cα-methyl-L-valine, we show that a well defined, solvent controlled, reversible 310-/α-Helix transition takes place even in a homo-oligomer as short as a terminally blocked hexapeptide. Homo-peptide sequences blocked as a urethane or an acetamide at the N-terminus and as a methyl ester or an N-alkyl amide at the C-terminus are all appropriate. The nature of the occurring helical species in the various solvents tested was assessed by electronic or vibrational circular dichroism. © 2008 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 90: 567–574, 2008. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com

  • peptide α 310 Helix dimorphism in the crystal state
    Journal of the American Chemical Society, 2007
    Co-Authors: Marco Crisma, Michele Saviano, Alessandro Moretto, Quirinus B Broxterman, Bernard Kaptein, Claudio Toniolo
    Abstract:

    The fully Cα-methylated homo-peptide Ac-[l-(αMe)Val]7-NHiPr is completely 310-helical when its crystals are grown from a methanol solution, whereas it is α-helical when crystallized from HFIP (1,1,1,3,3,3-hexafluoropropan-2-ol), thus providing an example of a solvent-driven α/310-Helix dimorphism in the crystal state. The interactions of cocrystallized HFIP molecules with the peptide in the α-helical structure are reported.

  • Peptide α/310-Helix Dimorphism in the Crystal State
    Journal of the American Chemical Society, 2007
    Co-Authors: Marco Crisma, Michele Saviano, Alessandro Moretto, Quirinus B Broxterman, Bernard Kaptein, Claudio Toniolo
    Abstract:

    The fully Cα-methylated homo-peptide Ac-[l-(αMe)Val]7-NHiPr is completely 310-helical when its crystals are grown from a methanol solution, whereas it is α-helical when crystallized from HFIP (1,1,1,3,3,3-hexafluoropropan-2-ol), thus providing an example of a solvent-driven α/310-Helix dimorphism in the crystal state. The interactions of cocrystallized HFIP molecules with the peptide in the α-helical structure are reported.

  • Two-Dimensional Infrared Spectral Signatures of 310- and α-Helical Peptides
    Journal of Physical Chemistry B, 2007
    Co-Authors: Hiroaki Maekawa, Claudio Toniolo, Quirinus B Broxterman, Nienhui Ge
    Abstract:

    Two-dimensional infrared (2D IR) spectra of Cα-alkylated model octapeptides Z-(Aib)8-OtBu, Z-(Aib)5-l-Leu-(Aib)2-OMe, and Z-[l-(αMeVal)]8-OtBu have been measured in the amide I region to acquire 2D spectral signatures characteristic of 310- and α-helical conformations. Phase-adjusted 2D absorptive spectra recorded with parallel polarizations are dominated by intense diagonal peaks, whereas 2D rephasing spectra obtained at the double-crossed polarization configuration reveal cross-peak patterns that are essential for structure determination. In CDCl3, all three peptides are of the 310-Helix conformation and exhibit a doublet cross-peak pattern. In 1,1,1,3,3,3-hexafluoroisopropanol, Z-[l-(αMeVal)]8-OtBu undergoes slow acidolysis and 310-to-α-Helix transition. In the course of this conformational change, its 2D rephasing spectrum evolves from an elongated doublet, characteristic of a distorted 310-Helix, to a multiple-peak pattern, after becoming an α-Helix. The linear IR and 2D absorptive spectra are much l...

Alessandro Moretto - One of the best experts on this subject based on the ideXlab platform.

  • 1h azepine 2 oxo 5 amino 5 carboxylic acid a 310 Helix inducer and an effective tool for functionalized gold nanoparticles
    Journal of Organic Chemistry, 2015
    Co-Authors: Sara Pellegrino, Alessandro Moretto, Andrea Bonetti, Francesca Clerici, Alessandro Contini, Raffaella Soave, Maria Luisa Gelmi
    Abstract:

    A new α,α-disubstituted constrained glutamine analogue has been designed to decorate gold nanoparticles and to induce a 310-Helix when inserted in peptides. Using an efficient “one-pot” asymmetric Schmidt reaction between 4-disubstituted-cyclohexanone and hydroxyalkylazides, 1H-azepine-2-oxo-5-amino-5-carboxylic acid was prepared. The main (R) isomer was inserted at the N-terminus in a very short peptide sequence (i.e., PhCO-(R)-Oxo-Azn-l-Ala-Aib-l-AlaNHMe) and a stable 310-Helix conformation was obtained, as verified by both NMR experiments and molecular dynamics (MD) simulations. Finally, the presence of the hydroxyl chain at the nitrogen atom of the ring allowed for the preparation of covered chiral gold nanoparticles.

  • first homo peptides undergoing a reversible 310 Helix α Helix transition critical main chain length
    Biopolymers, 2008
    Co-Authors: Alessandro Moretto, Fernando Formaggio, Quirinus B Broxterman, Bernard Kaptein, Timothy A Keiderling, Ling Wu, Claudio Toniolo
    Abstract:

    The difference in length between the more elongated peptide 310-Helix and the more compact α-Helix is about 0.4 A/residue. This property makes the 310-/α-Helix reversible conversion very promising as a molecular switching tool between the N- and C-terminal functions of a peptide backbone. In this work, using homo-peptides of various main-chain length, all based on the strongly helicogenic, Cα-tetrasubstituted α-amino acid Cα-methyl-L-valine, we show that a well defined, solvent controlled, reversible 310-/α-Helix transition takes place even in a homo-oligomer as short as a terminally blocked hexapeptide. Homo-peptide sequences blocked as a urethane or an acetamide at the N-terminus and as a methyl ester or an N-alkyl amide at the C-terminus are all appropriate. The nature of the occurring helical species in the various solvents tested was assessed by electronic or vibrational circular dichroism. © 2008 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 90: 567–574, 2008. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com

  • First homo‐peptides undergoing a reversible 310‐Helix/α‐Helix transition: Critical main‐chain length
    Biopolymers, 2008
    Co-Authors: Alessandro Moretto, Fernando Formaggio, Quirinus B Broxterman, Bernard Kaptein, Timothy A Keiderling, Ling Wu, Claudio Toniolo
    Abstract:

    The difference in length between the more elongated peptide 310-Helix and the more compact α-Helix is about 0.4 A/residue. This property makes the 310-/α-Helix reversible conversion very promising as a molecular switching tool between the N- and C-terminal functions of a peptide backbone. In this work, using homo-peptides of various main-chain length, all based on the strongly helicogenic, Cα-tetrasubstituted α-amino acid Cα-methyl-L-valine, we show that a well defined, solvent controlled, reversible 310-/α-Helix transition takes place even in a homo-oligomer as short as a terminally blocked hexapeptide. Homo-peptide sequences blocked as a urethane or an acetamide at the N-terminus and as a methyl ester or an N-alkyl amide at the C-terminus are all appropriate. The nature of the occurring helical species in the various solvents tested was assessed by electronic or vibrational circular dichroism. © 2008 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 90: 567–574, 2008. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com

  • peptide α 310 Helix dimorphism in the crystal state
    Journal of the American Chemical Society, 2007
    Co-Authors: Marco Crisma, Michele Saviano, Alessandro Moretto, Quirinus B Broxterman, Bernard Kaptein, Claudio Toniolo
    Abstract:

    The fully Cα-methylated homo-peptide Ac-[l-(αMe)Val]7-NHiPr is completely 310-helical when its crystals are grown from a methanol solution, whereas it is α-helical when crystallized from HFIP (1,1,1,3,3,3-hexafluoropropan-2-ol), thus providing an example of a solvent-driven α/310-Helix dimorphism in the crystal state. The interactions of cocrystallized HFIP molecules with the peptide in the α-helical structure are reported.

  • Peptide α/310-Helix Dimorphism in the Crystal State
    Journal of the American Chemical Society, 2007
    Co-Authors: Marco Crisma, Michele Saviano, Alessandro Moretto, Quirinus B Broxterman, Bernard Kaptein, Claudio Toniolo
    Abstract:

    The fully Cα-methylated homo-peptide Ac-[l-(αMe)Val]7-NHiPr is completely 310-helical when its crystals are grown from a methanol solution, whereas it is α-helical when crystallized from HFIP (1,1,1,3,3,3-hexafluoropropan-2-ol), thus providing an example of a solvent-driven α/310-Helix dimorphism in the crystal state. The interactions of cocrystallized HFIP molecules with the peptide in the α-helical structure are reported.