Purification and analysis of the major components of chum salmon protamine contained in insulin formulations using high-performance liquid chromatography.

A simple high-performance liquid chromatographic method has been developed for the rapid purification and analysis of protamine components contained in insulin formulations. Only a single step is needed to separate peptides whose compositions, sizes, and unusual isoelectric points (pI 13.8) are nearly identical. The method involves their isocratic separation on a reversed-phase column using a pH 2 phosphate buffer and a low acetonitrile content as an eluant. The purified chum salmon components were analyzed by amino acid analysis, solid-phase amino acid sequencing, carboxypeptidase B digests, insulin complexation analysis, and a mass spectrophotometric procedure which gives an accurate mass of the intact peptides. This HPLC purification technique may also be applicable to protamines and other highly basic peptides isolated from other sources.