From microscale phase screening to bulk evaporative crystallization of proteins

Protein phase diagrams obtained from material-efficient microscale phase screenings can be used successfully for designing a macroscale preparative protein crystallization process to gain the crystal morphology desired. In this experimental study, the phase behavior of three globular proteins: hen egg white lysozyme, bovine serum albumin, and alcohol dehydrogenase from Lactobacillus brevis, is evaluated by isothermal microbatch phase screenings in 96-well plates. Vacuum bulk evaporative crystallization experiments in the permissible temperature range are performed at physicochemical conditions based on the phase diagrams determined, and the products are compared to those of the microscale screenings in terms of morphology and size. Crystals of the desired morphology are obtained in evaporative crystallization, when the phase diagram shows a broad region of this morphology. Even multiple crystal types or both crystals and amorphous precipitate are obtained parallelly in evaporative crystallization, when this is predicted by the phase screening. Crystals that have grown together in the screenings appear as individual crystals in the macroscale experiments, and most of the crystals are substantially smaller due to agitation. The findings are expected to pave the way for a more systematic approach in macroscale protein crystallization.