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Isolated Gramicidin Peptides Probed by IR Spectroscopy
Author(s) -
Rijs Anouk M.,
Kabeláč Martin,
AboRiziq Ali,
Hobza Pavel,
de Vries Mattanjah S.
Publication year - 2011
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201100212
Subject(s) - gramicidin , chemistry , infrared spectroscopy , gramicidin s , spectroscopy , intramolecular force , ab initio quantum chemistry methods , ab initio , infrared , analytical chemistry (journal) , phase (matter) , spectral line , molecular vibration , amide , crystallography , molecule , stereochemistry , organic chemistry , optics , physics , membrane , biochemistry , quantum mechanics , astronomy
We report double‐resonant IR/UV ion‐dip spectroscopy of neutral gramicidin peptides in the gas phase. The IR spectra of gramicidin A and C, recorded in both the 1000 cm −1 to 1800 cm −1 and the 2700 to 3750 cm −1 region, allow structural analysis. By studying this broad IR range, various local intramolecular interactions are probed, and complementary IR modes can be accessed. Ab initio quantum chemical calculations are used to support the interpretation of the experimental IR spectra. The comparison of the calculated frequencies with the experimental IR spectrum probed via the strong infrared absorptions of all the amide groups (NH stretch, CO stretch and NH bend), shows evidence for a helical structure in the gas phase, which is similar to that in the condensed phase. Additionally, we show that to improve the spectral resolution when studying large neutral molecular structures of the size of gramicidin, the use of heavier carrier gas could be advantageous.