Reversed-phase high-performance liquid chromatography peptide mapping of bovine somatotropin

Reversed-phase high-performance liquid chromatography peptide mapping techniques have been used to examine the primary structure of bovine somatotropin (bSt) isolated from Escherichia coli modified by recombinant DNA techniques (rbSt) and from bovine pituitary (pbSt). Peptide fragments arising from tryptic digestion of bSt were separated on Baker wide pore C4 or C8 columns with linear gradients (acetonitrile-water with 0.1% trifluoroacetic acid). Major peaks eluted in a consistent order, but significant day-to-day variation in retention times was observed. Isolated peptide fragments were analyzed via acid hydrolysis followed by formation and separation of the phenylthiocarbamyl amino acids. These correspond to expected tryptic fragments.