Polarization-selective femtosecond Raman spectroscopy of low-frequency motions in hydrated protein films

We investigated the vibrational dynamics of proteins in amorphous hydrated films of lysozyme and myoglobin using polarization-selective time-domain Raman spectroscopy. The anisotropic spectra for these proteins all have a broad peak due to librational motion of side chains at 90 cm−1 and a background that may arise from bound water. The isotropic spectrum of lysozyme is similar to that of myoglobin, and has peaks at 240 and 500 cm−1 that are likely due to secondary structure fluctuations. These results suggest that low-frequency deformations of the protein molecule may contribute to the solvation dynamics of proteins in aqueous solution.