Crystals of gp11 grown under optimized conditions. (a) Crystal form A, grown in 1.6 M ammonium sulfate, 0.1 M trisodium citrate, and pH 5.7. Crystals are rhombohedral with a maximum edge length of 200 µm. (b) Crystals form B, grown in 1.0 M trisodium citrate, 0.1 M tris(hydroxymethyl)aminomethane (Tris), and pH 8.4. The truncated octahedron in the upper right measures approximately 150 µm × 150 µm × 50 µm. (c) Diffraction pattern for crystal form A, which indexed to space group P3x21. The resolution of the outermost ring is 3.63 Å. (d) Diffraction pattern for crystal form B, showing spots to ~2.8 Å, which indexed to P4x212. The resolution of the outermost ring is 3.32 Å.