Growth of Protein Crystal at Interface between Two Liquids Using Slow Cooling Method

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 wherein the crystals had no contact with a growth vessel. The long and narrow shape of the crystals indicated that they had grown at a lower supersaturation, leading to high crystallinity. This method also made it possible to remove the crystals easily without causing any mechanical damage. A large lysozyme crystal 2.5 mm in length was obtained in 25 days from a seed crystal kept at the interface. 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.