Isotope-edited FT-infrared spectra of the Amide I region of hexamer peptide isotopologues of alpha-aminoisobutyric acid (Z-Aib6-OtBu) have been collected in order to explore coupling between and among carbonyl stretches in the conformational context of 310 helices. Oligomers of Aib provide predominantly 310 helical structures, and isotopic enrichment of a carbonyl carbon with 13C lowers an amide I mode frequency by ~ 40 cm-1. The Amide I band is sensitive to the details of peptide secondary structure due to inter-carbonyl coupling. Infrared spectra and quantum chemical computational results for unlabeled, singly-labeled, and doubly-labeled isotopologues will be presented and discussed. FT-IR spectra using solvents such as dichloromethane (a nonpolar aprotic solvent) and methanol (a polar, protic solvent) allow the exploration of the effects of inter- and intramolecular hydrogen bonding. Coupling between carbonyl oscillators is revealed by the FT-IR lineshapes of the isotopologues and can be rationalized by the DFT calculations.

Isotope-edited FT-IR spectra of isotopologues of α-aminoisobutyric acid hexamer peptides

245th National Meeting (2013)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.