Pattern formation and coarsening during metastable phase separation in lysozyme solutions

We observed interesting structures during phase transformations of lysozyme solutions. The process begins with the separation of a protein-rich liquid phase in the form of droplets. The droplets fall to the bottom of the chamber in a few minutes, and on the scale of an hour they begin to merge, forming an interconnected spongelike structure. In the final transformation process, the sponge turns into crystals. The existence of the sponge phase depends upon the relative time scales for droplet coalescence and crystal nucleation, something we were able to vary by changing the salt concentration in our solution. We expect our observations to have significance for producing protein crystals for x-ray structure analysis of proteins.