Process for the purification or concentration of biologically active proteins, and appropriate means therefor

Zum Reinigen bzw. Anreichern von biologisch aktiven Proteinen versetzt man eine wässrige Lösung, die das gewünschte Protein enthält, bei einem pH-Wert unter dessen isoelektrischem Punkt mit einer solchen Menge eines arylsulfonsauren Azofarbstoffes mit zwei Sulfonatgruppen, die durch 8 bis 10 in Resonanzbeziehung stehende Doppelbindungen, unter welchen sich wenigstens eine N=N-Doppelbindung befindet, voneinander entfernt sind, bis zumindest der grösste Teil der biologischen Aktivität des gewünschten aktiven Proteins sich im Niederschlag befindet, trennt den Niederschlag und bringt das aktive Protein bei einem pH-Wert über seinem isoelektrischen Punkt wieder in Lösung. The present invention provides a process for the purification or enrichment of biologically active proteins by the addition of a selective precipitation agent, wherein an aqueous solution containing the desired protein is mixed at a pH value below its isoelectric point with such an amount of an arylsulphonic acid azo dyestuff with two sulphonate groups, which are separated from one another by 8 to 10 double bonds standing in resonance relationship, among which there is present at least one N=N double bond, that at least the greater part of the biological activity of the desired active protein is present in the precipitate, the precipitate is separated off and the active protein is again brought into solution at a pH value above its isoelectric point. The present invention also provides an agent for the selective precipitation of biologically active proteins from aqueous solutions thereof without the loss of the biological activity, wherein it contains or consists of an aryl sulphonic acid azo dyestuff with two sulphonate groups, which are separated from one another by 8 to 10 double bonds standing in resonance relationship, among which there is present at least one N=N double bond.