Is β-homo-proline a pseudo-γ-turn forming element of β-peptides? An IR and VCD spectroscopic study on Ac-β-HPro-NHMe in cryogenic matrices and solutions

Sándor Góbi, Krisztina Knapp, E. Vass, Zs. Majer, G. Magyarfalvi, M. Hollósi, G. Tarczay

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Abstract

In order to test the pseudo-γ-turn forming capability of β-homo-proline (β3-HPro) 2-[(2S)-1-acetylpyrrolidin-2-yl]- N-methylacetamide (Ac-β3-HPro-NHMe) was synthesized and its potential energy landscape was investigated by infrared (IR) and vibrational circular dichroism (VCD) spectroscopy combined with density functional calculations. Based upon a comparison between experimental and computed spectra three different pseudo-γ-turn-like trans conformers and a cis conformer were identified in low-temperature Ar and Kr matrices. The computations in agreement with the observations reveal that, in contrast to its α-Pro analogue, the room-temperature abundance of the cis conformer is significant, falling above 10% in the isolated phase. Furthermore, solution-phase vibrational spectra and computations show that the cis conformer is predominant in polar solvents. This result indicates that β3-HPro is significantly less apt to form pseudo-γ-turns when compared to the γ-turn forming tendency of α-proline. The present study also shows that the interpretation of solution-phase VCD spectra of flexible molecules should be done with extra caution.

Original languageEnglish
Pages (from-to)13603-13615
Number of pages13
JournalPhysical Chemistry Chemical Physics
Volume12
Issue number41
DOIs
Publication statusPublished - Nov 7 2010

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Proline
Cryogenics
dichroism
cryogenics
peptides
Circular dichroism spectroscopy
Infrared radiation
Vibrational spectroscopy
Peptides
Vibrational spectra
matrices
Potential energy
Density functional theory
falling
Temperature
vibrational spectra
Molecules
tendencies
potential energy
analogs

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Physics and Astronomy(all)

Cite this

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title = "Is β-homo-proline a pseudo-γ-turn forming element of β-peptides? An IR and VCD spectroscopic study on Ac-β-HPro-NHMe in cryogenic matrices and solutions",
abstract = "In order to test the pseudo-γ-turn forming capability of β-homo-proline (β3-HPro) 2-[(2S)-1-acetylpyrrolidin-2-yl]- N-methylacetamide (Ac-β3-HPro-NHMe) was synthesized and its potential energy landscape was investigated by infrared (IR) and vibrational circular dichroism (VCD) spectroscopy combined with density functional calculations. Based upon a comparison between experimental and computed spectra three different pseudo-γ-turn-like trans conformers and a cis conformer were identified in low-temperature Ar and Kr matrices. The computations in agreement with the observations reveal that, in contrast to its α-Pro analogue, the room-temperature abundance of the cis conformer is significant, falling above 10{\%} in the isolated phase. Furthermore, solution-phase vibrational spectra and computations show that the cis conformer is predominant in polar solvents. This result indicates that β3-HPro is significantly less apt to form pseudo-γ-turns when compared to the γ-turn forming tendency of α-proline. The present study also shows that the interpretation of solution-phase VCD spectra of flexible molecules should be done with extra caution.",
author = "S{\'a}ndor G{\'o}bi and Krisztina Knapp and E. Vass and Zs. Majer and G. Magyarfalvi and M. Holl{\'o}si and G. Tarczay",
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T1 - Is β-homo-proline a pseudo-γ-turn forming element of β-peptides? An IR and VCD spectroscopic study on Ac-β-HPro-NHMe in cryogenic matrices and solutions

AU - Góbi, Sándor

AU - Knapp, Krisztina

AU - Vass, E.

AU - Majer, Zs.

AU - Magyarfalvi, G.

AU - Hollósi, M.

AU - Tarczay, G.

PY - 2010/11/7

Y1 - 2010/11/7

N2 - In order to test the pseudo-γ-turn forming capability of β-homo-proline (β3-HPro) 2-[(2S)-1-acetylpyrrolidin-2-yl]- N-methylacetamide (Ac-β3-HPro-NHMe) was synthesized and its potential energy landscape was investigated by infrared (IR) and vibrational circular dichroism (VCD) spectroscopy combined with density functional calculations. Based upon a comparison between experimental and computed spectra three different pseudo-γ-turn-like trans conformers and a cis conformer were identified in low-temperature Ar and Kr matrices. The computations in agreement with the observations reveal that, in contrast to its α-Pro analogue, the room-temperature abundance of the cis conformer is significant, falling above 10% in the isolated phase. Furthermore, solution-phase vibrational spectra and computations show that the cis conformer is predominant in polar solvents. This result indicates that β3-HPro is significantly less apt to form pseudo-γ-turns when compared to the γ-turn forming tendency of α-proline. The present study also shows that the interpretation of solution-phase VCD spectra of flexible molecules should be done with extra caution.

AB - In order to test the pseudo-γ-turn forming capability of β-homo-proline (β3-HPro) 2-[(2S)-1-acetylpyrrolidin-2-yl]- N-methylacetamide (Ac-β3-HPro-NHMe) was synthesized and its potential energy landscape was investigated by infrared (IR) and vibrational circular dichroism (VCD) spectroscopy combined with density functional calculations. Based upon a comparison between experimental and computed spectra three different pseudo-γ-turn-like trans conformers and a cis conformer were identified in low-temperature Ar and Kr matrices. The computations in agreement with the observations reveal that, in contrast to its α-Pro analogue, the room-temperature abundance of the cis conformer is significant, falling above 10% in the isolated phase. Furthermore, solution-phase vibrational spectra and computations show that the cis conformer is predominant in polar solvents. This result indicates that β3-HPro is significantly less apt to form pseudo-γ-turns when compared to the γ-turn forming tendency of α-proline. The present study also shows that the interpretation of solution-phase VCD spectra of flexible molecules should be done with extra caution.

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