Influence of Vessel Surfaces on the Nucleation of Protein Crystals

Treatment of vessel surfaces is common practice in many protein crystallization protocols. The research reported here shows that such treatments can have a significant effect on the resulting kinetics of protein crystallization. Untreated and silanized low-protein-binding polystyrene wells were used in batch isothermal crystallization experiments with the model protein lysozyme. An automated photomicroscopy apparatus was used to measure the induction time as a function of supersaturation, and the corresponding nucleation kinetics were determined and modeled using classical nucleation theory. The use of silanized wells led to a transition from homogeneous nucleation to heterogeneous nucleation that is not observed for the untreated polystyrene wells. The silanizing compounds are similar to those used in high-performance liquid chromatography stationary phases for protein separations. While the silanizing compounds beneficially modify the surface tension in the crystallization vessels, they also inadvertently create a surface conducive to heterogeneous nucleation, which affects the interpretation of crystallization experiments.