Crystals of chIFNGR1. (a) Initial clusters of chIFNGR1 crystals. (b) Single crystals of chIFNGR1 were obtained after optimization in 20%(v/v) polyethylene glycol 5000 monomethyl ether, 0.1 M HEPES, 0.5 M sodium carbonate pH 7.0. Only the crystals with a sword-like shape were able to diffract X-rays to 2.0 Å resolution. (c) Cubic-shaped single crystals of chIFNGR1 were obtained using 1.26 M sodium phosphate monobasic monohydrate, 0.14 M potassium phosphate dibasic pH 5.6 but diffracted X-rays to less than 4 Å resolution.