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During the coagulation two prothrombin fragments are formed differing in molecular size and electrophoretic mobility but containing a common piece of the prothrombin molecule. The concentration of the smaller fragment is much lower than that of the larger fragment, but it is increased when the coagulation is accelerated by addition of tissue extract. On incubation in the presence of the blood cells, part of the bigger fragment is converted to a new similar component with a higher electrophoretic mobility.

SummaryEnd split products of fibrinogen after prolonged interaction with plasmin were separated on DEAE-cellulose. The D and E compounds measured with light ab- sorbancy constituted about 75% respectively 10% of the end split products.The D product was separated by electrophoresis into 8 components with slight difference in charge and all of them carried the same antigenic determinants. All components were found in plasmin digested fibrinogen prepared from a pool and from single donors. Four of the ∼D components were predominant. The sedimentation coefficient of the D preparation with these 4 components was 5.3 and the fraction sedimented as an homogenous peak. Slight heterogeneity of the preparation was, however, found on determination of the diffusion coefficient. The molecular weight was calculated as 80,000. On gel filtration of the D fraction on Sephadex G 200, the D products were eluted in the beginning of the albumin peak. It is suggested that the D product which is practically homogenous on ultracentrifugation dissociates on electrophoresis. The combination of the electrophoretic, immunologic and ultracentrifugal data suggests that the fibrinogen molecule consists of a series of similar repetitive units.The E product was homogenous in the ultracentrifuge and on electrophoresis. The sedimentation coefficient was 3.3 and the molecular weight was estimated to 40,800.On filtration through Sephadex G 200 the E product was hardly distinguishable from the D product and was eluted together with the ablumin.

SummaryPure fibrinogen and fibrinogen in plasma respectively, were digested with plasmin under various conditions. The split products obtained were afterwards separated on Sephadex G 200 and determined immunologically. The investigation showed that when plasmin digested plasma is separated by gel filtration high molecular weight split products with antigenic determinants for both D and E products occur in at least 3 different main types, which are eluted in the “19 S” and “7 S” peaks. On digestion of pure fibrinogen investigated in the same way only 2 main types of split products occurs in the same region. In the “4 S” peak D and E products occur as end degradation products.The amount of split products formed in serum samples with fibrinolysis is larger than in those with fibrinogenolysis.Split products in sera from patients with different diseases were identified after gel filtration on Sephadex G 200. As a rule, they were eluted together with the macro - globulins (“19 S”) but samples from patients with advanced fibrinolytic conditions were also found to have split products of lower molecular weight, which were eluted later in the “7 S” and “4 S” peaks.With the immunologic technique used split products in the serum can be determined down to a concentration of 0.5 mg/100 ml. Split products were found in a concentration between 1 and 45 mg/100 ml in certain patients with liver disease, blood disease, cancer and thrombosis, but not in any of the healthy subjects studied.