A differential scanning calorimetric study of chymotrypsin in the presence of added polymers

Scanning calorimetry measurements of different amounts of chymotrypsin in water alone gave a temperature of denaturation (T_d) value of 54°C. However, when high‐molecular‐weight poly(ethylene glycol) was added to aqueous solutions of chymotrypsin, the thermostability of the enzyme was enhanced. For example, the addition of 20% (w/w) of poly(ethylene glycol) of molecular weight of 100,000 increased the T_d/ value to 66°C. In toluene containing various amounts of added water, ethyl cellulose was used to improve the thermostability of chymotrypsin. For this system, a T_d value of 82°C was obtained with a 20% (w/w/) concentration of ethyl cellulose and 2% (v/v) of added water. Polymers in these solvents interact with water, which could otherwise denature the enzyme; polymers also from complexes with enzyme molecules to produce a more stable structure. © 1994 John Wiley & Sons, Inc.