Kinetics of the crystallization of canavalin by the measurement of the supersaturation decay

Proteins can be crystallized from pH buffered aqueous solutions of strong electrolytes. Using a dilatometer, we measured the rate of canavalin crystallization as a function of pH, salt concentration, temperature, and initial protein concentration.; The rate constant, k, is independent of the initial protein concentration, as is to be expected in the case of first order kinetics. Canavalin molecules in aqueous solutions are macromolecular ions whose charge depends upon pH. As the pH of the growth solution increases, the crystallization rate constant decreases. This occurs because the rate of crystallization is impeded by the electrostatic repulsion between like-charged macromolecular ions.; The rate constant increases with increasing salt concentration, which indicates that the electrostatic repulsion between macromolecular ions is weakened by Debye-Mickel plasma screening produced by an inert electrolyte.; By contrast, the rate constant decreases with increasing temperature, which suggest that canavalin crystallization follows a mechanism involving several elementary steps.