proteins can be prepared which exhibit higher specific activity than that afforded in previously known coagulant preparations the complex of the present invention is further characterized in that its specific activity cannot be increased further to any significant extent e g by a factor less than 3 if at all by digestion with u03b1 thrombin preferably the specific activity of the invention preparations exceeds that of purified human factor viii c by a factor of 3 to 5 and more advantageous by at least 10 times by 50 or even by 100 times the protein complex of the present invention and biological preparations thereof are characterized in that the enhanced activity described above remains present over a continuous period of at least about 10 minutes and preferably at least about 30 minutes of course activity will generally be stable for much longer the complex also possesses the immunological characteristics of a factor viii c protein i e it binds to an antibody for human factor viii c this can be ascertained for instance by growing a monoclonal antibody to factor viii c as described below attaching the antibody to an agarose column passing an aqueous solution of the complex through the column and assaying the resultant solution for factor viii c activity this example shows how factor viii c was purified from commercial concentrate and digested with purified u03b1 thrombin a monoclonal antibody to factor viii c was produced and used to identify viii c polypeptides at several selected points during the digestion portions of the digestion mixture were assayed for viii c coagulant activity and for protein bands using sds page purification of viii c all steps were at room temperature chemicals were reagent grade.