Noncovalent polymerization of mesogens crystallizes lysozyme: Correlation between nonamphiphilic lyotropic liquid crystal phase and protein crystal formation

Crystallization of proteins is important for fundamental studies and biopharmaceutical development but remains largely an empirical science. Here, we report the use of organic salts that can form a class of unusual nonamphiphilic lyotropic liquid crystals to crystallize the protein lysozyme. Certain nonamphiphilic organic molecules with fused aromatic rings and two charges can assemble into stable thread-like noncovalent polymers that may further form liquid crystal phases in water, traditionally termed chromonic liquid crystals. Using five of these mesogenic molecules as additives to induce protein crystallization, we discover that molecules that can form liquid crystal phases in water are highly effective at inducing the crystal formation of lysozyme, even at concentrations significantly lower than that required for forming liquid crystal phases. This result reveals an example of inducing protein crystallization by the molecular assembly of the additives, and is consistent with a new mechanism by which the strong hydration of an assembly process provides a gradual means to compete for the water molecules to enable solvated proteins to form crystals.