Isotope-edited FT-infrared spectra of the Amide I region of hexamers of a-aminoisobutyric acid (Z-Aib6-OtBu) have been collected in order to explore the effects of 13C=O enrichment on the FT-IR spectra in the conformational context of 310 helices. Oligomers of Aib are known to adopt predominantly 310 helical structures, even at short peptide lengths. The Amide I band is sensitive to the details of peptide secondary structure.  We have collected infrared spectra of isotopomers of hexamers of Aib (e.g., Z-Aib-Aib-Aib-Aib-Aib-Aib-OtBu, Z-Aib*-Aib-Aib*-Aib-Aib-Aib-OtBu, and Z-Aib*-Aib*-Aib-Aib-Aib-Aib-OtBu, Aib* = 13C enrichment at *C=O) in dichloromethane (a nonpolar aprotic solvent) and methanol (a polar, protic solvent) to examine the effects of carbon-13 enrichment on the spectra. Differences between the spectral lineshapes and isotopically-induced shifts (~40 cm-1) of the Amide I bands of these peptide isotopomers in these two solvents will be discussed and compared to quantum chemical calculations.

Isotope-edited infrared spectra of isotopomers of 3<sub>10</sub> helical peptides in organic solvents

244th National Meeting (2012)

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Isotope-edited infrared spectra of isotopomers of 310 helical peptides in organic solvents

Isotope-edited infrared spectra of isotopomers of 3₁₀ helical peptides in organic solvents