Thermodynamics of BPTI folding

A calorimetric study of the basic pancreatic trypsin inhibitor (BPTI) has been performed using the new generation of the adiabatic scanning microcalorimeters, operating in an extended temperature range of 5-130 degrees C. Precise measurements of the heat capacities of the native and unfolded states of BPTI show that the heat capacity change upon unfolding strongly depends on temperature; its value is maximal at about 50 degrees C and diminishes as the temperature is increased. The temperature dependencies of the enthalpy and entropy changes upon BPTI unfolding were found to be similar to those normally observed for other small globular proteins. The stability of BPTI has been correlated with its structure.