IR spectroscopy of structural changes of α-chymotrypsin related to the changes of function in organic solvents

To determine the variations in the secondary structure of α-chymotrypsin related to changes of function, we measure the ATR-FTIR spectra of the lyophilized enzyme, its solutions in normal and heavy water, tablets wetted in acetonitrile and cyclohexane, and suspensions in these solvents. The experimental results show that the most significant structural changes (a decrease in the content of α-helical fragments and an increase in the content of β-sheets) are related to the transition from the aqueous solution to the lyophilized sample. Similar but less developed structural changes are observed for the transition from the lyophilized sample to suspensions in organic solvents.