All SHP-1 variants, SHP-1 H422Q, SHP-1 E427A, and SHP-1 S418A were purified via a 5 mL HiTrap Q HP column attached above a 5 mL HiTrap SP HP column using an FPLC filtration system. Both columns were equilibrated with lysis buffer. The cell lysate was loaded onto the columns, the HiTrap Q HP column was removed after loading, and the HiTrap SP HP column was washed with lysis buffer until the absorbance at 280 nm was baselined. Elution for SHP-1 variants was processed using a 100% gradient with elution buffer containing 500 mM NaCl, 50 mM BisTris pH 6.5, 1 mM EDTA, 3 mM DTT, and 10% glycerol. Eluted fractions exhibiting absorbance at 280 nm were collected and tested with pNPP for phosphatase activity. Fractions that showed activity were assayed for purity on a 15% SDS-PAGE gel.