Human Coagulation Factor IX

Human coagulation factor IX was purified by two ion‐exchange chromatographies on DEAE‐Sephadex A‐50, heparin‐Sepharose chromatography, hydroxyapatite chromatography and immuno‐adsorbent technique. Factor IX was homogeneous by ordinary and sodium dodecylsulphate disc electrophoresis, N‐terminal amino acid analyses and ultracentrifugation and by immunological criteria. The following molecular data were observed: Sedimentation equilibrium indicated a molecular weight of 66 100 and sedimentation velocity gave S20, w= 3.97 S. A partial specific volume of v̄= 0.712 ml/g was calculated from the amino acid and carbohydrate composition. Sodium dodecylsulphate disc gel electrophoresis suggested a molecular weight of 65 000. Gel filtration indicated a Stokes radius of 4.08 nm, and ‘a molecular weight’ of 72 000, as well as a diffusion coefficient D20, w= 5.15 × 10−7 cm2 s−1 and a frictional ratio f/f0= 1.54. Tyrosine was the N‐terminal amino acid. The amino acid composition is described. Factor IX contained approximately 17.5% carbohydrate, which includes 4.7% hexose, 6.8%N‐acetylhexos‐amine and 6% sialic acid. Microheterogeneity of pure factor IX was demonstrated by isoelectric focusing. Th