Ultracentrifugal Separation of Coagulation Factors: Platelet Cofactors and Inhibitors

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Abstract
Platelet cofactor I (antihemophilic material) was prepared in partially purified form by methods described in the literature. Its activity could be inhibited with material obtained from plasma or serum by extraction with ether. By centrifuging plasma at 106,000 g for 6 hours it could be separated into 2 fractions with unlike properties as regards the blood coagulation mechanisms. When tested for platelet cofactor activity the top layer of plasma contained practically none while the bottom layer of plasma was very active. Ether extracts prepared from the top layer of plasma contained powerful platelet cofactor inhibitory material, whereas ether extracts from the bottom layer of plasma, prepared in the same way, did not possess this inhibitory activity in appreciable quantities.