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Home > Research Teams > Structure and Dynamics of Isolated Complex and Photoexcited Systems > Chirality and Spectroscopy > Spectrosccopy of cyclic dipeptides

Spectrosccopy of cyclic dipeptides

by Zehnacker-Rentien Anne - 3 August 2018 (modifié le 25 March 2020)

Cyclic dipeptides built on a diketopiperazine (DKP) ring and containing two aromatic residues of either identical or opposite chirality are spectroscopically studied in different environments. In the gas phase, conformer-specific laser spectroscopy under supersonic expansion conditions combined with quantum chemical calculations shows that the structure of the dipeptide containing phenylalanine (Phe), namely, cyclo Phe-Phe, shows little dependence upon the chirality of the residues. A similar geometry is observed for both LL and LD configurations, with one Phe folded over the DKP ring and the other one extended. The same lack of sensitivity is observed for cyclo TyrPro, despite the steric bias brought by the cylic proline. Two conformations indeed are observed, namely a folded geometry involving CH…π and an extended geometry involving an NH…π interaction. The strength of these two weak interactions slightly differ in the two diastereomers.
Families of Tyr-Pro cyclo structures, LL on the left and LD on the right
Families of Tyr-Pro cyclo structures, LL on the left and LD on the right

In contrast, very strong chirality dependence of the structure is observed for cyclo tyrosine-tyrosine, cyclo Tyr-Tyr. While both LL and LD diastereomers show the same “folded extended” structure as cyclo Phe-Phe, a structure involving a strong hydrogen bond between the hydroxyls of the two tyrosine residues is observed for LL only.

Homochiral cyclo Tyr-Tyr isomer with a tyrosine cycle folded over the peptide cycle
Homochiral cyclo Tyr-Tyr isomer with a tyrosine cycle folded over the peptide cycle
Homochiral cyclo Tyr-Tyr isomer with a hydrogen bond between hydroxyls
Homochiral cyclo Tyr-Tyr isomer with a hydrogen bond between hydroxyls

Publications

Conformational Study of the Jet-Cooled Diketopiperazine Peptide Cyclo Tyrosyl-Prolyl
A. Pérez-Mellor, I. Alata, V. Lepere, and A. Zehnacker
Journal of Physical Chemistry B, 2019, vol 123 (28), 6023-6033

Stereochemistry-dependent hydrogen bonds stabilise stacked conformations in jet-cooled cyclic dipeptides: (LD) vs. (LL) cyclo tyrosine–tyrosine
F. BenNasr, A. Pérez-Mellor, I. Alata, V. Lepere, N.-E. Jaïdane, and A. Zehnacker
Faraday Discussions, 2018, vol 212, 399-419

Chirality effects in the structures of jet-cooled bichromophoric dipeptides
A. Pérez-Mellor, I. Alata, V. Lepere, and A. Zehnacker
Journal of Molecular Spectroscopy, 2018, vol 349, 71-84

Vibrational circular dichroism of a 2,5‐diketopiperazine (DKP) peptide: Evidence for dimer formation in cyclo LL or LD diphenylalanine in the solid state
Ariel Pérez‐Mellor, Anne Zehnacker
Chirality, 2017, vol 29 (2), 89–96.

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