Anticoagulant properties of heparin fractionated by affinity chromatography on matrix-bound antithrombin III and by gel filtration

Heparin purified by affinity chromatography on anti-thrombin III-Sepharose has been studied by various methods. The specific activities of the materials obtained were in the range 170–230 units/mg as determined by a whole plasma clotting method and 360–780 units/mg as determined by a F.X_a inhibition method. Gel filtration of the material showed that there was a definite molecular size dependency of the specific activities and the activity profiles were markedly different when assay -ed by different methods. These features were also observed (at generally lower activities) with gel filtration fractions of commercial heparin. The possible conclusions regarding the mechanism of heparin anticoagulant action are discussed.