Growth of High-quality and Large Protein Crystals at Interface between Two Liquids Using Slow Cooling Method

Abstract

A new method has been developed to grow high-quality and large protein crystals. By a slow cooling method, tetragonal lysozyme crystals were grown from spontaneous nucleation at the interface of two liquids. The crystals had no contact with a growth vessel, which made it possible to remove crystals easily without causing any mechanical damage. The long and narrow shape of the crystals indicated that they had grown at a lower supersaturation, leading to high crystallinity. A large lysozyme crystal 3.0 mm in length was obtained in 20 days from a seed crystal kept at the interface. The stir with protein solution accelerated the growth of a protein crystal and prevented additional nucleation due to uniform concentration of the solution. The combination of growth at the interface between two liquids and controlled slow cooling is effective for the growth of high-quality and large protein crystals.