Infrared spectroscopy unfolded proteins

A. (2004) Nonlinear infrared spectroscopy of protein conformational change during thermal unfolding. J. Phys. Chem. B, 108, 15332. 

Prestrelski et al. (66) used IR to optimize lyophilization conditions for interleukin-2 (IL-2). The authors were able to show that proteins can unfold during lyophilization, and that altering the lyophilization conditions determines whether the proteins refold into the original conformation upon reconstitution. Dong et al. (67) provide a comprehensive review of the use of infrared spectroscopy for the study of the effects of lyophilization on proteins. 

One of the primary mechanisms of protein degradation is the loss of globular structure [118, 119]. This process, termed denaturation, leads to a partially or completely unfolded species which usually lacks any of the biological activity of the native protein. A variety of methods have been employed to monitor the denaturation of proteins, including fluorescence, infrared, nuclear magnetic resonance (NMR), and CD spectroscopy. As CD is very sensitive to changes in both secondary and tertiary structure, its application to the study of protein folding... 

Fourier transform infrared (FTIR) vibrational spectroscopy senses the hydrogen bonding pattern of the peptide bonds of a protein and can detect unfolding transitions in terms of changes in the secondary stmcture patterns. As compared to CD, which also senses secondary stmcture, FTIR is relatively more responsive to jS-sheet stmc-tures. A disadvantage of FTIR is that it requires a higher protein concentration and that it is more difficult to automate for titration experiments. 

---