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Updated: Jun 27, 2026

Spatial Separation of Molecular Conformers and Clusters
Published on: January 9, 2014
Spectroscopy and conformational preferences of gas-phase helices
Jaime A Stearns1, Caroline Seaiby, Oleg V Boyarkin
1Laboratoire de Chimie Physique Moléculaire, Ecole Polytechnique Fédérale de Lausanne, EPFL SB ISIC LCPM, Station 6, CH-1015, Lausanne, Switzerland.
Abstract:
We describe here a study of the spectroscopy of two peptides that we expect to be helical, Ac-Phe-(Ala)(5)-Lys-H(+) and Ac-Phe-(Ala)(10)-Lys-H(+), and one that we expect to be globular, Ac-Lys(H(+))-Phe-(Ala)(10), with the goal of identifying the spectral features characteristic of their secondary structure. Conformation-specific IR-UV double resonance spectroscopy in a cold ion trap, together with nitrogen-15 isotopic substitution, allow us to identify four conformers of the smaller helix. Infrared spectra in the OH and amide NH stretch regions, together with theoretical calculations, provide diagnostics of the presence of helical structure as well as details of the specific hydrogen bonding patterns within the helix. The assigned vibrational spectra presented here provide a benchmark for the ability of theory to predict the spectrum of a helical peptide.
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