F ourier Transform Infrared Spectroscopy in Peptide and Protein Analysis

Abstract Infrared (IR) spectroscopy is one of the two forms of vibrational spectroscopy, the other being Raman spectroscopy. IR spectroscopy measures absorptions of vibrating molecules and yields information about molecular structures and structural interactions. The development of computerized Fourier transform infrared (FTIR) techniques has opened up new dimensions in biological IR spectroscopy owing to the increase in achievable signal‐to‐noise ratios, wavenumber accuracy, and data aquisition rates, and the ability to perform measurements with strongly absorbing samples. High‐quality FTIR spectra can be obtained with relative ease and rapidly with very small amounts of sample in a variety of environments. Measurements of proteins in aqueous solution are almost routine now, and can be performed under equilibrium and nonequilibrium conditions. There are many IR absorption bands characteristic of peptide groups and amino acid side‐chain groups from which information on protein structures can be obtained. The information provided by FTIR spectroscopy may be a global one or highly specific for a single vibrating chemical group. In some cases, the usefulness of the method is limited by difficulties in extracting the structural information contained in the IR absorption bands.