A new membrane-based crystallization techniques: tests on lysozyme

The great importance of protein science both in industrial and scientific fields, in conjunction with the intrinsic difficulty to grow macromolecular crystals, stimulates the development of new observations and ideas that can be useful in initiating more systematic studies using novel approaches. In this regard, an innovative technique, based on the employment of microporous hydrophobic membranes in order to promote the formation of lysozyme crystals from supersaturated solutions, is introduced in this work. Operational principles and possible advantages, both in terms of controlled extraction of solvent by acting on the concentration of the stripping solution and reduced induction times, are outlined. Theoretical developments and experimental results concerning the mass transfer, in vapour phase, through the membrane are presented, as well as the results from X-ray diffraction to 1.7Å resolution of obtained lysozyme crystals using NaCl as the crystallizing agent and sodium acetate as the buffer. Crystals were found to be tetragonal with unit cell dimensions of a=b=79.1Å and c=37.9Å; the overall Rmerge on intensities in the resolution range from 25 to 1.7Å was, in the best case, 4.4%.