Figure 2.

Phase separation of pidan with decreasing protein packing fraction. We diluted pidan material from an initial packing fraction of 12% in increasing volumes of NaOH solution (pH 12.90). Photographs show the system through a range of packing fractions, with volume-spanning gels forming at packing fractions greater than 3.3% and liquid–liquid phase separation occurring at all packing fractions less than about 3.3%. Blue circles show the fraction of protein in the gelled or dense phase of the system as a function of packing fraction; the fraction of total protein forming the dense phase decreased with dilution of the system. This phase behavior is consistent with a patchy-particle system¹³ but not with an isotropic colloidal system. A patchy particle (green circles) interacts with others via certain patches (yellow circles) on the surface.