| X-RAY DIFFRACTION |
? |
298 |
Purified DDAH1 was concentrated to approximately 10 mg/mL using an Amicon-Ultra centrifugal filter device (10 kDa MWCO). The protein was crystallized at 25 C using the hanging drop method (Hampton Research, Aliso Viejo, CA) from 25 % (w/v) PEG6000, 0.1 M Tris-HCl, pH 8.2. Further optimization was done manually using a 1:1 well solution: DDAH1 stock solution ratio to improve crystal size and morphology. Crystals grew to their maximum size in 3 weeks and were harvested after approximately 25 days. To determine the structure of DDAH1 in complex with ligand, the crystals were transferred to a reservoir containing 20 uL of 20 mM of the ligand in the crystallization mother liquor (25% PEG 6000, 0.1 M Tris-HCl, pH 8.2) and soaked for 30 min. Before data collection, crystals with good size and morphology were transferred into a cryoprotection solution (Well Solution supplemented with 25 % (v/v) glycerol) for 1 to 5 seconds using a the cryoloop (Hampton Research, Laguna Niguel, CA). Individual hDDAH1:ligand crystals were flash frozen in liquid nitrogen before use. |
