Synthesis, purification, and chemical characterization of the amino-terminal 1-34 fragment of bovine parathyroid hormone synthesized by the solid-phase procedure.

Peptides prepared by solid-phase synthesis during a systematic study of structure-activity relations in parathyroid hormone have been subjected, after sequential purifications, to rigorous analysis of purity by a variety of analytical techniques including sequence analysis by the Edman procedure. The present paper undertakes a critical appraisal of the utility of different tests of peptide purity and the use of the procedures in guiding and monitoring optimal synthesis strategies. Sequence analysis of a peptide representing the amino-terminal 34 residues of bovine parathyroid hormone (bPTH-(1-34)) revealed the presence of at least 30% of contaminating error peptides which were undetected by other analytical procedures. The major contaminant was identified as a peptid in which glutamine at position 29 was deleted. A repeat synthesis using fluorescamine rather than ninhydrin to monitor the coupling reaction resulted in a preparation that lacked the contaminant resulting from deletion. These findings demonstrate the particular value of sequence analysis in the evaluation of purity of peptides synthesized by the solid-phase technique.