Pressure effects of crystallization of protein were studied with hen egg white lysozyme as a model protein. Direct observation with use of a diamond anvil cell revealed that the solubility of tetragonal form crystals increased and that the nucleation rate decreased with pressure. To conduct quantitative studies on the crystal growth rates, a novel technique was developed for the rapid solubility measurement under high pressures by two-beam interferometry. The solubility of tetragonal form crystals was determined as a function of temperature at 0.1, 50, and 100 Mpa. And that of orthorhbmbic ones was measured at 0.1 and 100 Mpa. It was shown that the solubility of the tetragonal crystals in-creases with pressure, while the solubility of the orthorhombic crystals decreases with increasing pressure. This tendency was discussed by considering the hydration of the molecular binding sites in the crystals. Normal growth rates were also measured as a function of supersaturation under high pressures. They decreased with pressure. It indicates that the surface growth kinetics depends on pres-sure significantly. The birth and spread model was applied to understand the pressure effects on the growth kinetics. It was found that increase in the average ledge surface energy of the two dimensional nuclei with pressure explained decrease in the growth rate.
