Solid‐phase peptide synthesis and biological activity of bovine thymopoietin II (bTP–11)

Bovine thymopoietin (bTP), a 49 amino acid polypeptide, was synthesized using Merrifield's solid‐phase peptide synthesis methodology. The polypeptide was purified using anion‐exchange chromatography and reversed‐phase HPLC and characterized by mass spectrometry and amino acid analysis of the full‐length peptide and of products derived from digestion with Staphylococcus aureus V8 protease. The biological activity of the synthesized product was tested in several assay systems. Synthetic bTP was found to induce the expression of Thy 1.2 antigen on T‐lymphocytes from athymic mice, in agreement with previous studies on the biological activity of endogenous bTP. Biological activity at skeletal muscle and neuronal nicotinic acetylcholine receptor sites, as reported by others for bTP, could not be confirmed in our studies. The absence of biological activity at nicotinic receptor sites may be related to the results of a recent report demonstrating the presence of a cobratoxin‐like molecule in preparations of natural bTP. These data indicate that synthetic peptides have an important role for the evaluation of the specificity of the biological activity of polypeptides.