title: FT-IR spectroscopy and density functional theory calculations of 13C isotopologues of the helical peptide Z-Aib6-OtBu.
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 3(10) helical peptide Z-Aib6-OtBu and seven (13)C-enriched analogues that vary only in the number and position(s) of (13)C═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 (13)C 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 (13)C enrichment of Z-Aib6-OtBu allows for examination of interamide coupling between two labeled amide functional groups, providing experimental evidence of interamide coupling in the context of 3(10) helical structure. Although the calculated and observed interamide couplings of Z-Aib6-OtBu are a few cm(-1) and less, the eight peptides exhibit distinct infrared spectra, revealing details of interamide coupling and residue level vibrational environments.
authors: Department of Chemistry and Biochemistry, Fairfield University , Fairfield, Connecticut 06824, United States.
authors: Timothy
authors: T
authors: Zeko
authors: Steven F
authors: SF
authors: Hannigan
authors: Timothy
authors: T
authors: Jacisin
authors: Matthew J
authors: MJ
authors: Guberman-Pfeffer
authors: Eric R
authors: ER
authors: Falcone
authors: Melissa J
authors: MJ
authors: Guildford
authors: Christopher
authors: C
authors: Szabo
authors: Kathryn E
authors: KE
authors: Cole
authors: Jessica
authors: J
authors: Placido
authors: Erin
authors: E
authors: Daly
authors: Matthew A
authors: MA
authors: Kubasik
mesh_terms: D000409:Alanine / Q000737:chemistry*; D000621:Aminoisobutyric Acids / Q000138:chemical synthesis / Q000737:chemistry*; D002247:Carbon Isotopes; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry*; D011789:Quantum Theory; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D000621:Aminoisobutyric Acids; D002247:Carbon Isotopes; D010455:Peptides; D000409:Alanine