IMPROVED DIFFRACTION OF ANTITHROMBIN CRYSTALS GROWN IN MICROGRAVITY

Crystals of antithrombin were grown both on earth and in microgravity aboard US Space Shuttle Flight STS-67. The quality of crystals grown i n both environments was highly variable and many could not be indexed. The microgravity crystals, however, generally diffracted better, as d emonstrated by a novel procedure that estimates the resolution of the Bragg scatter from single diffraction images, without requiring knowle dge of the cell dimensions of the crystal. Whereas the best earth-grow n crystals never diffracted beyond 3 Angstrom resolution, the best mic rogravity crystal diffracted to 2.6 Angstrom. The improvement, demonst rated here by a comparison of 23 microgravity and 12 earth-grown cryst als, is attributed to better ordered crystal growth in microgravity, a lthough other factors may have contributed also.