Prothrombin is purified by two absorptions on a barium citrate adsorbent, followed by decomposition of the adsorbents with a weak carboxylic cation-exchanger (Amberlite IRF-97), isoelectric precipitation (pH 4.7-4.9) and further purification by chromatography on Sephadex G-200 or IRC-50. Finally it is recrystallised from a 1% solution adjusted to pH 6.0-7.0 and partial lyophilisation to ca 1/5 to 1/10th volume and set aside at 2-5o to crystallise. Occasionally seeding is required. [Miller Biochemical Preparations 13 49 1971.]
