Many performance-enhancing drugs are available on the black market. This makes them easily available for cheating athletes but also a health risk due to poor quality, other ingredients than those declared on the label, or as a result of an insufficient clinical assessment.

Katja Walpurgis and colleagues, German Sport University, Cologne, have identified an unknown fusion protein from three confiscated unlabeled black market products obtained from independent sources. The protein consists of several protein tags, a thrombin cleavage site for their post-translational removal, and remnants of a multiple cloning site.

Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis revealed that the protein is an empty expression vector without the DNA insert of interest which probably results from a failed protein production.

The effects of such a fusion protein as well as the influence of protein tags on the human body are unclear.

• Detection of an unknown fusion protein in confiscated black market products,
  Katja Walpurgis, Oliver Krug, Andreas Thomas, Tim Laussmann, Wilhelm Schänzer, Mario Thevis,
  Drug Test. Analysis 2014, 6, 1117–1124.
  DOI: 10.1002/dta.1713