Modification of human HbS by iMet and acetyl-iMet in MetAP2 inhibitor treated Townes SCD mice. The N termini of α-globin (15 127 Da) and β^S-globin (15 839 Da) are modified with iMet (15 258 Da and 15 970 Da, respectively) or acetyl-iMet (15 300 Da and 16 012 Da, respectively) in Townes SCD mice treated with MetAP2 inhibitor. (A) LC-MS analysis of RBC lysates from Townes mice treated with vehicle does not show baseline globin modification. (B) Townes mice treated intraperitoneally with CKD-732, 3 mg/kg daily for 3 days, show extensive modification of α-globin and β-globin (50% total HbS modification). Similar results were obtained in 5 independent studies. (C) Repeated cation-exchange chromatography yields highly pure samples of modified HbS for x-ray crystallographic structure studies with a single modification on each globin. Sample shown is acetyl-iMet–β^S-globin (96.1%) and iMet–α-globin (86.6%).