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Article Dans Une Revue Amino Acids Année : 2021

A theoretical and experimental case study of the hydrogen bonding predilection of S-methylcysteine

Résumé

S-containing amino acids can lead to two types of local NH•••S interactions which bridge backbone NH sites to the side chain to form either intra-or inter-residue H-bonds. The present work reports on the conformational preferences of S-methyl-L-cysteine, Cys(Me), using a variety of investigating tools, ranging from quantum chemistry simulations, gas phase UV and IR laser spectroscopy, and solution state IR and NMR spectroscopies, on model compounds comprising one or two Cys(Me) residues. We demonstrate that in gas phase and in low polarity solution, the C-and N-capped model compound for one Cys(Me) residue adopts a preferred C5-C6γ conformation which combines an intra-residue N−H•••O=C backbone interaction (C5) and an inter-residue N−H•••S interaction implicating the side-chain sulfur atom (C6γ ). In contrast, the dominant conformation of the C-and N-capped model compound featuring two consecutive Cys(Me) residues is a regular type I β-turn. This structure is incompatible with concomitant C6 interactions, which are no longer in evidence. Instead, C5γ interactions occur, that are fully consistent with the turn geometry and additionally stabilize the structure. Comparison with the thietane amino acid Attc, which exhibits a rigid cyclic side chain, pinpoints the significance of side chain flexibility for the specific conformational behavior of Cys(Me).
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Dates et versions

hal-03186714 , version 1 (31-03-2021)

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Venkateswara Rao Mundlapati, Zeynab Imani, Gildas Goldsztejn, Eric Gloaguen, Valérie Brenner, et al.. A theoretical and experimental case study of the hydrogen bonding predilection of S-methylcysteine. Amino Acids, 2021, 53 (4), pp.621-633. ⟨10.1007/s00726-021-02967-z⟩. ⟨hal-03186714⟩
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