Detection of His-tagged Long-R³-IGF-I in a black market product

Performance-enhancing substances are illicitly used in elite or amateur sports and may be obtained from the black market due to a cheaper and easier availability. Although various studies have shown that black market products frequently do not contain the declared substances, enormous amounts of illegally produced and/or imported drugs are confiscated from athletes or at customs with alarming results concerning the outcome of the analyses of the ingredients. This case report describes the identification of His-tagged Long-R³-IGF-I, which is usually produced for biochemical studies, in an injection vial.

The ingredients were isolated by immunoaffinity purification and identified by nano-UPLC, high-resolution/high accuracy mass spectrometry of the intact and trypsinated substance and by an enzyme-linked immunosorbent assay.

(Tandem) mass spectra characterized the protein as Long-R³-IGF-I with a His₆-tag attached to the C-terminus by the linker amino acids Leu-Glu.

His-tags are commonly added to proteins during synthesis to allow a convenient and complete purification of the final product and His-tags are subsequently removed by specific enzymes when being attached to the N-terminus. The effects of His-tagged Long-R³-IGF-I in humans have not been elucidated or described and the product may rather be a by-product from biochemical studies than synthesized for injection purposes.