[Contribution to the isolation and study of the molecular weight of human factor VIII].

The authors describe some properties of highly-purified factor VIII concentrates isolated from human plasma. The fraction containing "factor VIII-complex" (factor VIII procoagulant activity, factor VIII related antigen and von Willebrand factor) is homogeneous by analytical ultra-centrifugation and its sedimentation coefficient is (see article). By gel filtration in high ionic strength buffer a low molecular weight fraction (LMW) with factor VIII procoagulant activity stronger than plasma's one has been isolated. This LMW fraction contains neither factor VIII related antigens nor von Willebrand factor. Its molecular weight determined by gel filtration is approximately 250,000.