Macroscale production of crystalline interferon alfa-2b in microgravity on STS-52

Macroscale crystallization of zinc interferon alfa‐2b was achieved on STS‐52 in October 1992 in the Protein Crystallization Facility. Conditions for crystallization were established by adapting a microscale vapor diffusion method to a macroscale temperature induction method. A series of earth based pilot experiments established conditions to reproducibly crystallize zinc interferon alfa‐2b in high yield and under cleanroom conditions. As a control for the STS‐52 mission, a ground experiment was run simultaneously and in the same configuration as the flight experiment. Greater than 95% of the available protein crystallized in both the ground and flight experiments. Using a battery of physical, biochemical and biological characterization assays, demonstrated that sample processing, polysulfone bottle confinement and the conditions used for crystallization did not have a negative effect on protein integrity. Redissolved crystals from the flight and ground experiments showed full biological activity in a cytopathic effect inhibition assay as compared to an interferon control standard. Morphometric analysis comparing the overall length and width of the derived crystals showed a 2.4 fold increase in the length and width of the space grown crystals as compared to earth grown crystals. Space grown crystals have remained a stable free flowing suspension for over 2 years. Based on these results, further experiments are envisioned to investigate macroscale crystallization of biologically active macromolecules in microgravity.