Protein crystallization

Co-crystals of WT Spy 29-124 and Spy H96L 29-124 in complex with Im7 variants and casein were grown by vapor diffusion. 25–130 mg/ml dimer Spy was incubated with various Im7 or casein substrates at concentrations ranging from equimolar to three-fold excess substrate in 22%–33% PEG 3000, 0.88–1.0 M imidazole pH 8.0, and 40–310 mM zinc acetate at 20 °C. Crystals were flash frozen in liquid nitrogen using 35% PEG 3000 as a cryo-protectant. It is worthwhile to note that the flash freezing could somewhat bias the conformations observed in the crystal structure³⁶. However, we chose to freeze the crystal to provide us with the maximum capability to identify and interpret the iodine anomalous signals.