Erik Jorpes

On the assay of thrombin preparations.

Different techniques of assaying thrombic activity have been compared. The relative strength of three commercial thrombin preparations has been compared with that of an arbitrary standard. Heparinized plasma as used by Burstein and Guinand and TAME, toluene‐sulphonyl‐arginine methyl ester, as used by Sherry and Troll are both unsuitable as clotting substrates. Only purified fibrinogen can be used. Fibrinogen prepared according to M. and B. Blombäck proved to be suitable, giving only 3–7 per cent error in the thrombin determinations. It is suggested that the strength of the thrombin standard should be expressed by its capacity to split N‐terminal glutamic acid from fibrinogen with the appearance of N‐terminal glycine.