Elucidation of residue-level structure and dynamics of polypeptides via isotopp-edited infrared spectroscopy

Infrared spectroscopy is a powerful tool for analyzing the structure of proteins and peptides. The amide I band is particularly sensitive to the strength and position of the hydrogen bonds that define secondary structure as well as dipole-dipole interactions that are affected by the geometry of the peptide backbone. The introduction of a single C-13-labeled carbonyl into a peptide backbone results in a resolvable shoulder to the main amide I band, which can be analyzed as a separate peak. Thus, site-specific structural information can be obtained by sequential, systematic labeling of the backbone. This method of isotope-edited infrared spectroscopy is a tool for obtaining medium-resolution information about the backbone confromation and dynamics. This tool has been used to dissect the conformation and dynamics of a helices and amyloid aggregates, where the versatility of possible sampling with infrared spectroscopy is well-suited for studies of large-protein aggregates.