bath and held at 60 u00b0 c for 10 hours to pasteurize after pasteurization the plasminogen activity was 7 06 cln units ml this is translated to a recovery of plasminogen of 7 06 7 65 which is 93 200 ml of pasteurized plasminogen prepared according to the procedure of example 1 having 12 52 mg ml was applied to a sephadex g 50 column 5 0 u00d7 5 8 cm was equilibrated with ph 7 4 buffer solution containing 0 1m lysine 0 05m nacl 0 01m na 2 hpo 4 and 0 01m citric acid the same buffer solution was used to elute plasminogen molecules which was eluted at void volume and yielded 300 ml with 8 71 cln units ml the total activity applied to the column was equal to 2504 cln units and the total yield activity was 2613 2504 or 104 although it is obvious that this cannot be precisely correct it is within the range allowed for error a purified human plasminogen solution was prepared by affinity chromatography as in example 1 this plasminogen solution was stored at 70 u00b0 c for one month then thawed at 4 u00b0 c protein concentration was 2 42 mg ml plasminogen activity was 13 7 cln units ml total volume was 2450 ml the protecting agent was lysine ethyl ester 180 gms of this agent was dissolved in 1550 ml of buffer solution containing 0 1m lysine 0 05m nacl 0 01m na 2 hpo 4 0 01m citric acid then added to the plasminogen solution to make a total volume of 4000 ml and protein concentration became 1 48.