Abstract
Crystals of thaumatin and of lysozyme from turkey and hen egg white have been prepared in batch at 20Ā°C under hydrostatic pressures in the 0.1ā220 MPa range. The latter model protein served as a reference in this comparative study. Crystallization was performed in an agarose gel in contrast to former studies under pressure that were conducted in solution. After depressurization, the habit, number, length, shape and solubility of crystals were compared to those of control crystals that were prepared at atmospheric pressure (0.1 MPa). For the three proteins, the number of the crystals increases with pressure. For thaumatin and hen lysozyme, crystal length decreases but for turkey lysozyme it increases. While the solubility of the first protein decreases, that of both lysozymes increases. The relationship between solubility and pressure is linear in the three cases. The crystallization volumes Ī V are ā11 cm 3 mol ā1 for thaumatin, +15 cm 3 mol ā1 for turkey lysozyme and +3 cm 3 mol ā1 for hen lysozyme. For the lysozymes, they are explained by pressure-dependent conformational changes. The structure of thaumatin appears to be less deformable under pressure.
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