Factor Va generation during coagulation in normal and hemophilia C blood at 25 pmol/L initiator, with and without replacement. For the experiments described in Fig 3, analysis of factor V activation was performed by immunoblotting. Profiles following factor Va heavy chain (A) and light chain (B) were constructed by densitometric analysis as in the Materials and Methods. Time courses are given for formation of the heavy and light chains in normal blood (○) and hemophilia C blood (patient C1), with (□) and without (▵) factor XI replacement. Clot times are as in Table 1 and Fig 3, and curves have been drawn through the points by hand.