Theory of protein crystal nucleation and growth controlled by solvent evaporation

The driving force for protein crystallization is the supersaturation. In th e case of crystal growth in a hanging drop, the supersaturation at early ti mes is controlled by the dynamics of solvent evaporation and is largely ind ependent of the rate of appearance of the crystals. This permits the equati ons of Johnson, Mehl, Avrami, and Kolomogrov to be integrated using the cla ssic model for crystal nucleation and the spiral dislocation model for crys tal 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 thes e formulae include either explicitly or implicitly the protein mass, temper ature, pH, and ionic strength, which are the independent variables known ex perimentally to influence the overall rate of protein crystallization. (C) 1999 Published by Elsevier Science B.V. All rights reserved.