Boehringer Mannheim Gmbh

Waldemar Thum

Hellmuth Vetter

Gotthilf Naher

Gunter Lang

Peter Scheibe

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.dbd.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.dbd.N double bond.

Process for the purification or enrichment of biologically active

Storage-stable aqueous cholesterol oxidase compositions comprising cholestrol oxidase, a buffer and from 2 to 3.5 M sodium or potassium chloride as a stabilizing agent, are significantly superior to conventional compositions with respect to storage stability and fungibility.

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Tutzing, Germany

Waldemar Thum