FAR-INFRARED SPECTRUM OF CRYSTALLINE LYSOZYME

The far‐ir absorption spectrum of lysozyme was measured at room and liquid‐nitrogen temperatures. Dried layers of single crystals of tetragonal lysozyme chloride with a diameter of 100–300 μm were grown on a silicon plate. Such single‐crystalline samples were considered to have the following advantages in obtaining far‐ir spectra: (1) surface scattering is reduced, (2) the protein molecules are closely packed, and (3) air‐drying of the crystals reduces the number of water molecules without considerably changing the original configuration. The spectrum obtained consisted of a strong background absorption and a number of absorption peaks that were not clearly observed with the sample in the form of lyophilized powder. The peaks were ascribed to various delocalized vibrations of the main and side chains in the molecule. The peaks were also compared with the positions of Raman lines. The uniform background was assigned to the water molecules remaining in the crystals. Copyright © 1979 John Wiley & Sons, Inc.