Changes in the Reactivity of Purified Prothrombin After Freeze Drying. ∗

Summary

Purified prothrombin can be dried from the frozen state without immediate loss of activity. Thereafter progressive loss of prothrombin activity occurs, characterized by refractivity to the action of calcium plus thromboplastin plus Ac-globulin. In about one year most of the prothrombin is altered and in addition some is insoluble in aqueous solution. Prothrombin altered as the result of the freeze drying technic can be activated autocatalytically in 25% sodium citrate solution. The altered prothrombin has essentially the same electrophoretic properties as purified prothrombin and represents a derivative of prothrombin not previously described.