Chapter 5 - Macromolecular crystal growth: Surface kinetics and morphological studies

Abstract

This chapter presents a mathematical model to handle the complex phenomena related to the growth or resolution of protein crystals according to the protein concentration and solubility distribution in the feeding solution, taking into account the mass variation (and the morphological evolution) of the crystal because of the incorporation of nutrients and the possibility of (faceted) surface-orientation-dependent growth. It also explains the complex interplay and relative importance of the surface-attachment kinetics and the mass transport (diffusive and/or convective) in the liquid phase. It describes a novel numerical technique to investigate the combined effect of crystal growth and gravitational convection and, in particular, the interaction of this motion with the concentration field around the crystal and with the growth rates. No simplifying assumptions (such as Stokes flow, “a priori” imposed ambient flows, or “fixed” crystal size) are assumed in the development of the model. It elucidates the major differences between inorganic and organic crystal growth. Such an effort has a two-fold purpose: an attempt to create a link between the chapter and the earlier ones and to introduce the field of macromolecular crystallization. While an extensive body of theory and experimental results is available for the crystal growth rate analysis of low molecular weight species, there is less experimental data for higher molecular weight material and, in particular, for the crystallization of proteins.