Merck, SRE0003-25MU, Thrombin from bovine plasma

Biochem/physiol Actions
Serine protease that selectively cleaves Arg-Gly bonds in fibrinogen to form fibrin and fibrinopeptides A and B.
Analysis Note
Activity is expressed in NIH units obtained by direct comparison to a NIH Thrombin Reference Standard, Lot K.
The NIH assay procedure uses 0.2 mL of diluted plasma (1:1 with saline) as a substrate and 0.1 mL of thrombin sample (stabilized in a 1% buffered albumin solution) based on a modification of the method of Biggs. Only clotting times in the range of 15-25 seconds are used for determining thrombin concentrations.
Other Notes
Activity is expressed in NIH units obtained by direct comparison to a NIH thrombin reference standard.