Crystallization and phase transformation of protein crystals: A case study of lysozyme

摘要

The crystallization and phase transition of hen egg white lysozyme (HEWL) was investigated. Two modifications with favorable morphology and good enzymatic activity were obtained by batch crystallization, which were verified by X-ray powder diffraction. Tetragonal lysozyme crystals were found to appear at an alkaline pH at low temperatures as well as in acid buffer. A low temperature orthorhombic (LTO) morphology was obtained at room temperature. Phase transition was found to occur between the two modifications. Tetragonal crystals appeared in the basic buffer at low temperature and transferred to other modification when temperature increased. While in acid buffer, the orthorhombic crystals dissolved and tetragonal crystals appeared and remained in the solution.