Second anion exchange chromatography step during purification of protein C from plasma. Barium citrate eluate originating from 260 mL patient plasma (•) or 200 mL normal plasma (□) was applied to a column with 4 mL Q Sepharose FF. Elution of proteins was performed with a linear gradient from 0.18 to 0.50 mol/L NaCl (dotted line). Fractions (1 mL) were collected and analyzed for protein C(immunological). Fractions pooled and subjected to further purification by RP-HPLC (see Fig 2) are indicated by bars and denoted A, T, and D (patient) and t (normal subject). A quantity of 1 U/L of protein C(immunological) corresponds to the mean concentration in normal plasma.