Differential scanning calorimetry of proteins under high pressure

Calorimetric performance of a high pressure applicator for MC-2 micro-calorimeter (Microcal Inc. MA) was characterized. Irreversible denaturation under high pressure, up to 100MPa, was investigated for egg white lysozyme, bovine pancreas alpha-chymotripsin, bovine pancreas ribonucrease A and bovine hemoglobin. The high pressure application increased denaturation temperatures of lysozyme and alpha-chymotripsin. It did not change the temperature of ribonucrease but decreased it of hemoglobin. An equation is proposed to estimate activation volume of the irreversible denaturation from the difference between the denaturation profiles obtained at different pressures.