Theory of protein crystal nucleation and growth controlled by solvent evaporation

The driving force for protein crystallization is the supersaturation. In the case of crystal growth in a hanging drop, the supersaturation at early times is controlled by the dynamics of solvent evaporation and is largely independent of the rate of appearance of the crystals. This permits the equations of Johnson, Mehl, Avrami, and Kolomogrov to be integrated using the classic model for crystal nucleation and the spiral dislocation model for crystal growth. As results one obtains a formula for the number of crystals in the drop and another formula for their average size. The parameters in these formulae include either explicitly or implicitly the protein mass, temperature, pH, and ionic strength, which are the independent variables known experimentally to influence the overall rate of protein crystallization. (C) 1999 Published by Elsevier Science B.V. All rights reserved.