Laser‐Raman spectroscopy of biomolecules 16‐temperature dependence of the conformation of crystalline ribonuclease a from x‐ray diffraction and Raman spectroscopy

X-ray diffraction and Raman spectra have been studied for crystalline ribonuclease A as a function of temperature, up to 50°C for diffraction and 70°C for the spectra. Changes in the geometry of hydrogen-bonded tyrosines, disulfide groups and methionine side chains have been followed by means of the x-ray diffraction results, and the corresponding effects on the Raman spectra have been ascertained. The temperature trend of the Raman spectra of the crystalline enzyme corresponds surprisingly closely to that observed by Chen and Lord for the aqueous enzyme. It appears that intermolecular forces in the crystal are less important to the temperature stability of the enzyme than intramolecular forces. The close correspondence of the crystalline and aqueous temperature trends enables conformational changes in the crystal which affect the Raman spectrum to be identified with corresponding changes in aqueous conformation as shown by the aqueous Raman spectrum.