Low-frequency vibrational spectroscopy of proteins with different secondary structures.

Fourier transform infrared (FTIR) and Raman spectra of proteins with significantly different structures are measured in a spectral interval of 50 to 500 ?? cm ? 1 and noticeable spectral differences are revealed. Intensities of several spectral bands correlate with contents of secondary structure elements. FTIR spectra of superhelical proteins exhibit developed spectral features that are absent in the spectra of globular proteins. Significant differences of the Raman spectra of proteins that are not directly related to the difference of the secondary structures can be due to differences of tertiary and/or quaternary structure of protein molecules.