Crystallization within agarose gel in microgravity improves the quality of thaumatin crystals

To prevent crystals from moving in orbit and sedimenting upon their return to earth, the model protein thaumatin was crystallized in agarose gel in the Advanced Protein Crystallization Facility during the eight-day Space Shuttle mission STS-95 (November 1998). The quality of tetragonal crystals grown in microgravity was compared with that of controls prepared in parallel in the laboratory. On the basis of their diffraction properties, microgravity crystals were more ordered than crystals grown in gel on earth (the latter being, on average, better than reference crystals obtained in solution on earth). It is concluded that protein crystallization within a gel in microgravity may yield crystals of superior quality by combining the advantages of both environments. A possible explanation for the positive effect of microgravity on protein crystallization in gels involving the better quality of the nucleus is discussed.