LIGAND-EXCHANGE CHROMATOGRAPHY OF SMALL PEPTIDES ON COPPER(II)-MODIFIED SILICA-GEL - APPLICATION TO THE STUDY OF THE ENZYMATIC DEGRADATION OF METHIONINE-ENKEPHALIN

A copper(II)-modified silica gel has been used for the high-performances liquid chromatography of small peptides, isomeric dipeptides and glycine oligomers. This packing combines the high selectivity of the ligand-exchange procedure withthe high column efficiency obtained with microparticles of silica (7 μm). The capabilities of this new packing are shown by the separation of fragments of methionine-enkephalin, which is a neuroendocrine pentapeptide (Tyr-Gly-Gly-Phe-Met). Two isocratic systems have been used in conjunction, the first for the separation of Met-enkephalin tetrapeptides, tripeptides and Phe-Met, and the second for that of dipeptides and amino acids. These systems allowed the separation of all possible fragments of Met-enkephalin with an analysis time of about 15 min. It is then easy to observe the appearance and evolution of peptidic fragments following enzymatic degradation. Moreover, direct injection of the enzymatic media can be performed without storage of the frozen samples. © 1979.