The phase diagram and the pressure-temperature behavior of proteins

The pressure and temperature behavior of proteins is discussed in the framework of the phase diagram. This gives unique information on the changes in heat capacity, thermal expansion and compressibility of protein unfolding. It also relates the cold, heat and pressure denaturation. The difference in pressure- and temperature-induced aggregation of unfolded proteins shows the unique features of pressure effects. A molecular interpretation of the thermodynamic quantities is not possible on the basis of model systems unless the packing defects are taken into account. High pressure molecular dynamic calculations contribute in a unique way to our understanding of pressure effects.