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Issue 36, 2017
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The role of amino acid side chains in stabilizing dipeptides: the laser ablation Fourier transform microwave spectrum of Ac-Val-NH2

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Abstract

The steric effects imposed by the isopropyl group of valine in the conformational stabilization of the capped dipeptide N-acetyl-L-valinamide (Ac-Val-NH2) have been studied by laser ablation molecular beam Fourier transform microwave (LA-MB-FTMW) spectroscopy. The rotational and quadrupole coupling constants of the two 14N nuclei determined in this work show that this dipeptide exists as a mixture of C7 and C5 conformers in the supersonic expansion. The conformers are stabilized by a C[double bond, length as m-dash]O⋯H–N intramolecular hydrogen bond closing a seven- or a five-membered ring, respectively. The observation of both conformers is in good agreement with previous results on the related dipeptides containing different residues, confirming that the polarity/non-polarity of the side chains of the amino acid is responsible for the conformational locking/unlocking. The voluminous isopropyl group is not able to prevent the less stable C5 conformer from forming but it destabilizes the C[double bond, length as m-dash]O⋯H–N interaction.

Graphical abstract: The role of amino acid side chains in stabilizing dipeptides: the laser ablation Fourier transform microwave spectrum of Ac-Val-NH2

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Publication details

The article was received on 13 Jun 2017, accepted on 17 Aug 2017 and first published on 18 Aug 2017


Article type: Paper
DOI: 10.1039/C7CP03924G
Citation: Phys. Chem. Chem. Phys., 2017,19, 24985-24990
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    The role of amino acid side chains in stabilizing dipeptides: the laser ablation Fourier transform microwave spectrum of Ac-Val-NH2

    I. León, E. R. Alonso, S. Mata, C. Cabezas, M. A. Rodríguez, J.-U. Grabow and J. L. Alonso, Phys. Chem. Chem. Phys., 2017, 19, 24985
    DOI: 10.1039/C7CP03924G

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