| X-RAY DIFFRACTION |
7 |
295.5 |
Initial crystallization screening was performed around conditions previously reported (31, 48) by dispensing 0.2 + 0.2 mL sitting drops with a Phoenix robotic liquid handling system (Art Robbins) on 96-well plates.
Once optimal crystallization conditions were determined, crystals were grown by the sitting-drop vapor-diffusion method using drops dispensed by the Phoenix with 1- to 2-mL ribosome complexes
mixed with 1-2 mL of reservoir solution [100 mM Tris-OAc, pH 7.0, 200 mM potassium thiocyanate (KSCN), 3.6-5% PEG 20,000, 6-14% 2-methyl-2,4-pentanediol (MPD)] at 22.5C.
Crystals emerged after 5-7 d and matured between 2-3 wk. Crystals were then subjected to cryoprotection by gradually replacing the mother liquor with cryoprotection buffer I
(100 mM Tris-OAc, pH 7.0, 200 mM KSCN, 5% PEG 20,000, 25% MPD, 14% PEG 200, and 10 mM Mg(OAc)2). The crystals then were flash-frozen by plunging into liquid nitrogen. |
