MW: 555.1. Purity 98.9% by HPLC. The plasmin substrate provide by our company is chemically and functionally identical to Chromogenix S-2251. Each 25 mg of substrate is lyophilized with 60 mg mannitol as a bulking agent. For best results add 4.5 ml of I mM HCI directly to vial to make a 10mM stock solution then aliquot and freeze. Dilute 1:50 in PBS or TBS to make an 0.2mM working solution. Add 0.1 ml test sample to 0.9 ml substrate and monitor color development at 405nm.