Matthew A. Kubasik, Timothy Zeko, Steven F. Hannigan
Jan 28, 2014
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Influential Citations
2
Citations
Journal
Biophysical Journal
Abstract
Isotope-edited FT-IR spectroscopy is a combined synthetic and spectroscopic method used to characterize local (e.g., residue-level) vibrational environments of biomolecules. We have prepared the 310 helical peptide Z-Aib6-OtBu and seven 13C-enriched analogues which vary only in the number and position(s) of 13C=O isotopic enrichment. FT-IR spectra of these eight peptides solvated in the nonpolar aprotic solvent dichloromethane have been collected and compared to frequency, intensity, and normal mode results of DFT calculations. Single 13C enrichment of amide functional groups tends to localize Amide I vibrational eigenmodes, providing residue-specific information regarding the local environment (e.g., hydrogen bonding or solvent exposure) of the peptide bond. Double 13C enrichment of Z-Aib6-OtBu allows for examination of inter-amide coupling between two labeled amide functional groups, providing experimental evidence of inter-amide coupling in the context of 310 helical structure. Although the calculated and observed inter-amide couplings of Z-Aib6-OtBu are a few cm−1 and less, the eight peptides exhibit distinct infrared spectra, revealing details of inter-amide coupling and residue level vibrational environments.