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Structure et dynamique des systèmes complexes isolés photoexcités (SYSIPHE) >
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2023
2023
Peer-reviewed Publications |
Imani, Z., Mundlapati, V. R., Brenner, V., Gloaguen, E., Le Barbu-Debus, K., Zehnacker, A., Robin, S., Aitken, D. J., & Mons, M. (2023). Non-covalent interactions reveal the protein chain δ conformation in a flexible single-residue model. ChemComm, .
Résumé: The δ conformation is a local secondary structural feature in proteins that implicates a πamide N-H···N interaction between a backbone N atom and the NH of the following residue. Small molecule probes of this conformation have been limited so far to rigid proline-type models that may over-emphasize the significance of the interaction. We show here that, in thiacyclic amino acid derivatives with a sulphur atom in the γ-position, specific side-chain/backbone N-H···S interactions stabilize the δ conformation sufficiently to allow it to compete with classical C5 and C7 H-bonding conformers. With support from quantum chemistry, the δ-folded conformers have been characterized by IR spectroscopy in the gas phase. In solution, the IR absorption of the πamide N-H appears at 3450 cm-1, notably less red-shifted than in proline-type models, in a frequency range often considered as implicating a free NH motif and suggestive of very weak hydrogen bonding at best.
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