Digestion of fibrinogen in the presence of calcium with plasmin. Fibrinogen (N: normal fibrinogen, P: patient fibrinogen) was treated with plasmin in Tris-buffered saline containing 2 mM calcium (A) or increasing concentrations of calcium or 2 mM EDTA (B) at 37°C for 1 hour. Untreated fibrinogen and plasmin digests of fibrinogen were analyzed by SDS-PAGE under nonreducing conditions. Fragments D1, D2A, and D3 are indicated. The relative amounts of Tokyo V fibrinogen fragments D2A and D3 were quantified by densitometry, and were approximately 17.5% of the sum of fragments D1, D2A, and D3 (mean of 2 experiments).