High and low affinity heparin (HA and LA heparin) were prepared from commercial heparin by affinity chromatography to insolubilized antithrombin III. HA heparin was radiolabeled with 35S and subdivided by gel chromatography into high molecular weight (HMW, average 17,000-26,000 daltons), intermediate molecular weight (MMW, average 12,000-13,000 daltons), low molecular weight (LMW, average 5,000...