An investigation on the effect of evaporation rate on protein crystallization

One well-known prerequisite for successful crystallization from solution is a supersaturated solution. To achieve supersaturation, many methods are known, among which solvent evaporation is a common approach. For protein crystallization, the most widely used method is vapor diffusion, in which solvent evaporation from the crystallization solution is the major reason for achieving supersaturation. The solvent evaporation rate may affect the actual concentration distribution in the crystallization solution, thereby influencing the crystallization process. To explore the effect of evaporation rate on protein crystallization, we used lysozyme as a model protein and studied the crystallization success rate at different evaporation conditions. Successful crystallization occurred only when both supersaturation and evaporation rates were in suitable ranges. This study demonstrates that both supersaturation level and the rate of reaching supersaturation (or solvent evaporation rate) are important for lysozyme crystallization. To increase the chance of obtaining crystals, manipulation of solvent evaporation rate is one choice. According to this assumption, we performed crystallization screening trials at different evaporation rates using three model proteins. The trials demonstrate that control of the evaporation rate during crystallization may provide more opportunities to obtain crystals.