Membrane crystallization of macromolecular solutions

Crystal growth is the critical step in determining the protein X-ray crystal structure. Hundreds, or even thousands, of crystallization trials must often be performed on a target macromolecule and, unfortunately, less than 1% of them typically yield promising results. Many macromolecules are reluctant to crystallize and, usually, their crystalline arrangement is not good enough to provide diffraction data at a resolution sufficient to establish structure-function correlation. The history of macromolecular crystallization emphasizes the importance of new observations and ideas that are useful in initiating more systematic studies using novel techniques and creative approaches. On this basis an innovative methodology, the membrane crystallization, has been introduced in order to promote the formation of macromolecular crystals. Lysozyme crystals, produced by removing the solvent (in vapour phase) from the protein solution by using microporous hydrophobic membrnaes, showed a good structural quality suitable for successive X-ray diffraction analysis.

In this work an innovative technology, the membrane crystallization, was employed to obtain protein crystals from supersaturated solutions. In addition to the classical parameters, nucleation and growth rates were also easy controlled by varying concentration and flow-rate of the stripping solution: as result, good quality crystals appeared both in few hours and in some weeks. At present, the experimental activity carried out on Lysozyme evidenced the difficulty intrinsically connected to the general problem of the protein crystallization to find an optimal operative protocol. At the same time, preliminary results confirm the interesting potentialities of this new approach to the macromolecular crystallization.