Controlling one protein crystal growth by droplet-based microfluidic system.

The preparation of a single crystal is important for a detailed understanding of the structure of protein. However, the preparation of a suitable crystal for X-ray diffraction is often a drawback due to the complexity of the protein molecules and the limited fundamental understanding of the protein crystallization mechanism. In this study, we studied the crystallization mechanism in droplet that was prepared by the microfluidic chip. We found that the mechanism of crystal growth in droplet is different from that by a conventional microbatch method. One crystal was grown in one droplet by controlling droplet shape and droplet volume. In addition, the surface area in droplet affected the size of the obtained protein crystal and the number of crystal(s). The growth of the (110) and (101) faces of tetragonal crystal could be determined by studying one crystal formed within one droplet, indicating that the observation and evaluation of one crystal growth kinetics is easily carried out compared with the conventional method.