FTIR and CD spectroscopic detection of H-bonded folded polypeptide structures

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Abstract

The FTIR spectra of a selection of cyclic and linear peptides were measured in DMSO and TFE. The backbone conformation in DMSO of the cyclic models has been inferred from ROESY-based interproton connectivities and the temperature coefficients of the NH protons. The FTIR measurements give support to the following assignment of low-frequency amide I bands: > 1645cm-1, open (weakly H-bonded) β- and γ-turns; ≃ 1640 cm-1, β-turns (1 ← 4 H-bonded); ≃ 1625 cm-1, γ-turns (1 ← 3 H-bonded); <1620 cm-1, β- and γ-turns with bifurcated H-bondings. Solvent-dependence studies on the diamide models Ac-Xxx-NHCH, (8, Xxx = Pro, Ala and Gly) suggest that it is the inverse γ-turn (C7/(cq)) structure which is capable of forming a strong 1 ← 3 intramolecular H-bond (band at ≃ 1625 cm-1). DMSO destroys 1 ← 3 IHBs of γ-turns and bifurcated turn systems even in cyclic peptides but does not affect 1 ← 4 IHBs. TFE has a stabilizing effect on both 1 ← 4 and 1 ← 3 H-bondings which gives rise to mixtures of β and γ-turn conformers. Contrary to vibrational spectroscopy, circular dichroism can differentiate between type I(III) and type II β-turns showing class C and class B CD spectra, respectively. Based on the above findings, a class C CD spectrum measured in TFE can reflect the predominance of type I(III) β-turn conformation, but it may also be a composite of subspectra of H-bonded β-turn and γ-turn as well as open conformers.

Original languageEnglish
Pages (from-to)47-56
Number of pages10
JournalJournal of Molecular Structure
Volume408-409
DOIs
Publication statusPublished - Jun 1 1997

Fingerprint

polypeptides
Polytetrafluoroethylene
Fourier Transform Infrared Spectroscopy
Dimethyl Sulfoxide
Cyclic Peptides
Peptides
peptides
Conformations
Diamide
Vibrational spectroscopy
Circular Dichroism
Amides
amides
dichroism
Protons
Spectrum Analysis
low frequencies
Temperature
composite materials
protons

Keywords

  • β-turn
  • γ-turn
  • Bifurcation
  • FTIR
  • H-bonding

ASJC Scopus subject areas

  • Structural Biology
  • Organic Chemistry
  • Physical and Theoretical Chemistry
  • Spectroscopy
  • Atomic and Molecular Physics, and Optics

Cite this

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title = "FTIR and CD spectroscopic detection of H-bonded folded polypeptide structures",
abstract = "The FTIR spectra of a selection of cyclic and linear peptides were measured in DMSO and TFE. The backbone conformation in DMSO of the cyclic models has been inferred from ROESY-based interproton connectivities and the temperature coefficients of the NH protons. The FTIR measurements give support to the following assignment of low-frequency amide I bands: > 1645cm-1, open (weakly H-bonded) β- and γ-turns; ≃ 1640 cm-1, β-turns (1 ← 4 H-bonded); ≃ 1625 cm-1, γ-turns (1 ← 3 H-bonded); <1620 cm-1, β- and γ-turns with bifurcated H-bondings. Solvent-dependence studies on the diamide models Ac-Xxx-NHCH, (8, Xxx = Pro, Ala and Gly) suggest that it is the inverse γ-turn (C7/(cq)) structure which is capable of forming a strong 1 ← 3 intramolecular H-bond (band at ≃ 1625 cm-1). DMSO destroys 1 ← 3 IHBs of γ-turns and bifurcated turn systems even in cyclic peptides but does not affect 1 ← 4 IHBs. TFE has a stabilizing effect on both 1 ← 4 and 1 ← 3 H-bondings which gives rise to mixtures of β and γ-turn conformers. Contrary to vibrational spectroscopy, circular dichroism can differentiate between type I(III) and type II β-turns showing class C and class B CD spectra, respectively. Based on the above findings, a class C CD spectrum measured in TFE can reflect the predominance of type I(III) β-turn conformation, but it may also be a composite of subspectra of H-bonded β-turn and γ-turn as well as open conformers.",
keywords = "β-turn, γ-turn, Bifurcation, FTIR, H-bonding",
author = "E. Vass and S. Holly and Zs. Majer and J. Samu and I. Laczk{\'o} and M. Holl{\'o}si",
year = "1997",
month = "6",
day = "1",
doi = "10.1016/S0022-2860(96)09493-8",
language = "English",
volume = "408-409",
pages = "47--56",
journal = "Journal of Molecular Structure",
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T1 - FTIR and CD spectroscopic detection of H-bonded folded polypeptide structures

AU - Vass, E.

AU - Holly, S.

AU - Majer, Zs.

AU - Samu, J.

AU - Laczkó, I.

AU - Hollósi, M.

PY - 1997/6/1

Y1 - 1997/6/1

N2 - The FTIR spectra of a selection of cyclic and linear peptides were measured in DMSO and TFE. The backbone conformation in DMSO of the cyclic models has been inferred from ROESY-based interproton connectivities and the temperature coefficients of the NH protons. The FTIR measurements give support to the following assignment of low-frequency amide I bands: > 1645cm-1, open (weakly H-bonded) β- and γ-turns; ≃ 1640 cm-1, β-turns (1 ← 4 H-bonded); ≃ 1625 cm-1, γ-turns (1 ← 3 H-bonded); <1620 cm-1, β- and γ-turns with bifurcated H-bondings. Solvent-dependence studies on the diamide models Ac-Xxx-NHCH, (8, Xxx = Pro, Ala and Gly) suggest that it is the inverse γ-turn (C7/(cq)) structure which is capable of forming a strong 1 ← 3 intramolecular H-bond (band at ≃ 1625 cm-1). DMSO destroys 1 ← 3 IHBs of γ-turns and bifurcated turn systems even in cyclic peptides but does not affect 1 ← 4 IHBs. TFE has a stabilizing effect on both 1 ← 4 and 1 ← 3 H-bondings which gives rise to mixtures of β and γ-turn conformers. Contrary to vibrational spectroscopy, circular dichroism can differentiate between type I(III) and type II β-turns showing class C and class B CD spectra, respectively. Based on the above findings, a class C CD spectrum measured in TFE can reflect the predominance of type I(III) β-turn conformation, but it may also be a composite of subspectra of H-bonded β-turn and γ-turn as well as open conformers.

AB - The FTIR spectra of a selection of cyclic and linear peptides were measured in DMSO and TFE. The backbone conformation in DMSO of the cyclic models has been inferred from ROESY-based interproton connectivities and the temperature coefficients of the NH protons. The FTIR measurements give support to the following assignment of low-frequency amide I bands: > 1645cm-1, open (weakly H-bonded) β- and γ-turns; ≃ 1640 cm-1, β-turns (1 ← 4 H-bonded); ≃ 1625 cm-1, γ-turns (1 ← 3 H-bonded); <1620 cm-1, β- and γ-turns with bifurcated H-bondings. Solvent-dependence studies on the diamide models Ac-Xxx-NHCH, (8, Xxx = Pro, Ala and Gly) suggest that it is the inverse γ-turn (C7/(cq)) structure which is capable of forming a strong 1 ← 3 intramolecular H-bond (band at ≃ 1625 cm-1). DMSO destroys 1 ← 3 IHBs of γ-turns and bifurcated turn systems even in cyclic peptides but does not affect 1 ← 4 IHBs. TFE has a stabilizing effect on both 1 ← 4 and 1 ← 3 H-bondings which gives rise to mixtures of β and γ-turn conformers. Contrary to vibrational spectroscopy, circular dichroism can differentiate between type I(III) and type II β-turns showing class C and class B CD spectra, respectively. Based on the above findings, a class C CD spectrum measured in TFE can reflect the predominance of type I(III) β-turn conformation, but it may also be a composite of subspectra of H-bonded β-turn and γ-turn as well as open conformers.

KW - β-turn

KW - γ-turn

KW - Bifurcation

KW - FTIR

KW - H-bonding

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U2 - 10.1016/S0022-2860(96)09493-8

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