For laboratory use only. S-2222 is a chromogenic substrate for Factor Xa. It is also very sensitive to trypsin. The substrate has been used for the determination of Factor X in plasma, Factor Xa in plasma, Factor Xa inhibitor in plasma, Heparin in plasma, Factor VIII in plasma, Coagulating enzyme from horseshoe crab plasma, Trypsin in duodenal fluid. The substrate is also sensitive to subtilisin, acrosin and Factor XIIa but insensitive to most other enzymes tested, e.g. Factor IXa, kallikrein (glandular and plasma) and papain-like enzymes.