“…Frequently it might be difficult to get an approval for tagged biopharmaceuticals. For example, the most commonly used polyHis-tag can be used for fast and easy purification by immobilized metal ion affinity chromatography (Franzreb et al, 2006;Premsukh et al, 2011). The inevitable (and subsequent) proteolytic cleavage of these tags might, however, be expensive or difficult to achieve (Gottschalk, 2009).…”