Izit crystal dye

The complex crystal of S-GAT Fab and corresponding drug was prepared by co-crystallization method with a molar ratio of 1 : 10. All the crystals were generated by the vapor diffusion method in sitting drops at 20 °C. Initial crystal screening was performed with 8 kits: JCSG core I, JCSG core II, JCSG core III, JCSG core IV, JCSG classic, JCSG +, PEGs I and PEGs II (QIAGEN, Hilden, Germany). The protein drops for initial crystal screening contained 0.1 μL Fab fragment and 0.1 μL reservoir solution were dispersed on 96-weill plates using Mosquito (TTP LabTech, Royston, U.K.). The crystals obtained by screening were determined as protein crystals by using Izit Crystal Dye (Hampton Research, Aliso Viejo, CA, U.S.A.), and then the corresponding conditions were optimized by adjusting the buffer pH and the precipitant concentration. The protein drops for optimization contained 1 μL Fab fragment and 1 μL reservoir solution, and crystals appeared after 30 d. The optimized reservoir condition of the S-GAT Fab apo form crystal contained 1.6 M ammonium sulfate, 24% glycerol and 0.8 M sodium acetate, pH 4.6. The optimized reservoir condition of S-GAT Fab crystal in complex with S-GAT (S-GAT Fab complex) contained 0.2 M sodium chloride, 1.4 M ammonium sulfate and 1 M sodium acetate, pH 4.9.