Thermodynamic and kinetic considerations for crystal growth of complex molecules from solution

Abstract

A general thermo-kinetic picture of crystallization from a nutrient phase is presented in terms of the driving force available in both the far field and interface regions. The necessary and sufficient boundary value problems that must be solved to correct the far field thermodynamic state variables to the interface state variables is sketched and the material parameters needed to describe the processes for small molecules identified. Extension of this modeling approach to protein crystallization is made with the recognition that small crystallites and large molecules in aqueous solution may behave like colloid particles with an accompanying electrical double layer. Thus, the concepts and numerics of colloid stability theory should probably be considered when dealing with protein crystallization. Key constraints on controlled crystallization in this case involve (a) the controlled passage of the molecules from the secondary potential minimum to the primary potential minimum of the crystal interface double layer, (b) the simultaneous partial electrolyte/solvent stripping and protein particle incorporation into the crystal, and (c) the bulk solvent neutralization of the incremental electrolyte and pH changes due to crystallization so that a steady state potential distribution may be maintained in the interface region.