Summary
1. Platelet fibrinogen has been purified from washed bovine platelets. The procedure
was based on the methods for purification of plasma fibrinogen by fractionated precipitations
and extractions with ethanol and glycine below 0°, and precipitation of proteins by
dimethylformamide at 0°.
2. The platelet extract obtained by freezing and thawing of the cells, freed from
insoluble material by centrifugation at 23,000 x g for 30 min, contained 0.22 ±0.003mg
fibrinogen per 109 platelets. Total protein of this fraction was 0.77 ±0.08 mg per 109 platelets whereas that of the insoluble fraction was 0.79 ±0.09 mg per 109 platelets.
3. The most purified platelet fibrinogen fraction contained 91-98% of the protein
in a thrombin-clottable state. The yield was approx. 20%. It showed homogeneity in
analytical ultracentrifugation, in immunoelectrophoresis using an antiserum produced
by immunization of rabbits against platelet extract, and in starch gel electrophoresis
using a discontinuous system of Tris HCl and borate buffers offering a high resolution
power towards the platelet proteins. Polyacrylamide disc electrophoresis revealed
two to three faint lines behind the main fibrinogen line. At least one such line was
also observed with purified plasma fibrinogen.