The DNA was transformed into BL21-DE3 cells and grown overnight at 37 °C on an LB culture plate containing 100 ng/µL kanamycin monosulfate for WT SHP-1, or 100 ng/µL ampicillin for the SHP-1 variants. One colony was selected and placed into 10 mL of SOC media containing 100 ng/µL kanamycin monosulfate or ampicillin and grown overnight. The following morning, 1 L of LB media containing 100 ng/µL kanamycin monosulfate or ampicillin was inoculated with the 10 mL of overnight growth and shaken at 170 rpm at 37 °C until the OD600nm reached 0.6-0.8. After the optimal OD was reached, the 1 L growth was induced by 0.1 mM isopropyl β-d-thiogalactoside (IPTG) and shaken at 170 rpm at room temperature overnight. The cells were harvested by centrifugation at 12,000g for 30 min at 4 °C and stored at -80 °C.