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Issue 14, 2010
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Conformations and vibrational spectra of a model tripeptide: change of secondary structure upon micro-solvation

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Abstract

Mid-infrared (IR) hole burning spectra of the model tripeptide Z-Aib-Pro-NHMe (Z = benzyloxycarbonyl) in gas phase and its micro-clusters with one and two methanol molecules are presented. To establish a relation between experimental spectra and the underlying conformations, calculations at the DFT [B3LYP/6-311++G(d,p)] level of theory are performed. In particular, the intra-peptide and the peptidemethanol hydrogen bonds can be identified from spectral shifts in the amide I, II, and III regions. While the unsolvated tripeptide as well as its one-methanol cluster prefer a γ-turn structure, a β-turn structure is found for the two-methanol cluster, in agreement with previous condensed phase studies. Comparison of measured and simulated spectra reveals that the favorable methanol binding sites are at the head and tail parts of the tripeptide. The interconversions between γ-turn and β-turn structures are governed by potential barriers below 10 kJ mol−1 inside one of the low energy basins of the potential energy surface.

Graphical abstract: Conformations and vibrational spectra of a model tripeptide: change of secondary structure upon micro-solvation

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Article information


Submitted
15 Dec 2009
Accepted
29 Jan 2010
First published
23 Feb 2010

Phys. Chem. Chem. Phys., 2010,12, 3415-3425
Article type
Paper

Conformations and vibrational spectra of a model tripeptide: change of secondary structure upon micro-solvation

H. Zhu, M. Blom, I. Compagnon, A. M. Rijs, S. Roy, G. von Helden and B. Schmidt, Phys. Chem. Chem. Phys., 2010, 12, 3415
DOI: 10.1039/B926413B

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