The Effect Of Packing Density On Membrane Crystallization Of Lysozyme

X-ray diffraction is a good method for determining the 3D structure of a protein, the protein crystals for X-ray diffraction are needed. Unfortunately, many macromolecules are reluctant to crystallize, and usually, their lattice is not regular enough to provide diffraction data. Generally, the crystallization methods of small molecules are not suitable for the crystallization of biomacromolecules. Therefore, access to a perfect protein crystal has become the main bottleneck of the structure determination of proteins. It's necessary to develop a new method obtaining a perfect protein crystal. Crystals of biomacromolecules, which are suitable for X-ray diffraction, can be obtained by membrane crystallization technology.The PVDF hollow fiber microporous membrane modules with three packing densities were employed to study the influences of the flow velocities of crystallization solution and stripping agent on membrane crystallization of lysozyme. It was found that, due to the different fiber distribution of membranes modules, the increase of flow velocity of crystallization solution in the appropriate range can't improve effectively the transmembrane flux at a lower packing density(12.4%), and moreover, it had little effect at a higher packing density(24.7%).Transmembrane flux increased as flow velocity of stripping agent increased at different packing density. For the module with lower packing density, high quality crystals have been prepared under the proper flow velocities of crystallization solution and stripping agent.The membrane modules with the same three packing densities were employed to study the influences of vacuum tightness of downstream side and the flow velocities of crystallization solution on membrane crystallization of lysozyme. The results showed that adjusting the vacuum (0.6KPa for membrane modules with 12.4% and 18.6% packing density, and 0.2KPa for membrane module with 24.7% packing density) to ensure the transmembrane flux, in order to improve the quality of crystals, the flow velocities of crystallization solution should be slowdown, and the additives such as glycerol and DMSO can be added into the crystallization solutions.At last, The PTDE tabulate membrane modules were employed to research the membrane crystallization of lysozyme. Taking into account the shape of lysozyme crystals and the crystal size distribution, when the precipitants (NaCl) concentration is 4%, the optimal operating conditions is the initial lysozyme concentration of 20mg/ml, the stripping solution (MgCl2) concentration of 20%.