Hydrostatic pressure is a useful parameter to control protein crystallization. One can change the solubility of protein crystals quickly by changing pressure. Information about the hydration of the specific surfaces of protein molecules can be obtained from the pressure dependency of solubility. When a protein molecule is hydrophobic or when its molecular volume in a solution is significantly larger than that in a crystal, applying high pressure is expected to be an effective method to promote crystallization. Pressure also affects the growth kinetics of protein crystals. Dependency of a growth rate on a driving force for crystallization was measured on typical proteins and analyzed using a two-dimensional nucleation growth model of a poly-nuclei type. High-pressure effects on growth kinetics could be explained by changes in a surface free energy, an activation energy and an average distance between kinks. Common understanding, however, has not yet been obtained for growth kinetics.
