Pressure and concentration dependence of nucleation kinetics for crystallization of subtilisin

Nucleation kinetics of subtilisin was studied as a function of supersaturat ion (10-70 mg/ml) and pressure (0.1-34 MPa). The nucleation was found to ha ve a 1.6 order dependence on supersaturation. Extent of nucleation decrease d by a factor of 60 as the pressure increased from 0.1 to 34 MPa. High pres sure was also used as a probe to understand the nucleation behavior of subt ilisin and an estimation of the pressure-dependence of nucleation rate prov ided a value of 330 cm(3)/mol for the activation volume for nucleation. The residues in the contact region were determined to be hydrophilic by protei n structure analysis. Responsible mechanisms are hypothesized. (C) 2000 Els evier Science B.V. All rights reserved.