| dc.description.abstract | Two-dimensional infrared spectroscopy (2D IR) is commonly used to identify peptide secondary structures via the amide I mode. While each secondary structure displays a unique frequency range, additional work is required to localize structural elements onto specific regions of the peptide. The most common approach is the use of 13C18O-labels in the carbonyl backbone, which can be used to quantify vibrational couplings between specific residues and thus obtain single residue structural information. In extended structures such as such as β-sheet rich amyloid fibrils, additional information can be extracted without the use of labels via transition dipole strength calculations, which are more sensitive to ordering and vibrational delocalization than frequency alone. Furthermore, some of the vibrational modes within proteins can overlap, particularly modes from infrared active sidechains. The use of waiting times in conjunction with 2D IR spectroscopy allows these modes to be differentiated by their inherent vibrational lifetimes. A combination of these techniques was used to characterize amylin-nanoparticle interactions, determine the impact of mutations on insulin B9-23 fragments, and establish a robust isotope labeling scheme for α-helical peptides. | |
