Effects of microgravity on the crystal quality of a collagen-like polypeptide

(Pro-Pro-Gly)(10) is one of the most widely studied collagen polypeptide mo dels. Microgravity crystal growth of (Pro-Pro-Gly)(10) was carried out in t he Advanced Protein Crystallization Facility aboard the Space Shuttle Disco very during the STS-95 mission. Crystals were successfully grown in all exp eriments, using both dialysis and free-interface diffusion methods. The qua lity of the microgravity-grown crystals and of ground-grown counterparts wa s assessed by X-ray synchrotron diffraction. Microgravity-grown crystals ex hibited a significant improvement in terms of dimensions and resolution lim it. As previously reported, crystals were orthorhombic, space group P2(1)2( 1)2(1) However, the diffraction pattern showed weak reflections, never prev iously measured, that were consistent with new unit-cell parameters a = 26. 9, b = 26.4, c = 182.5 Angstrom. This allowed the derivation of a new model for the arrangement of the triple-helical molecules in the crystals.