SEPARATION OF A BIOACTIVE CYCLIC PEPTIDE AND ITS OLIGOMERIC FORMS BY MICELLAR ELECTROKINETIC CHROMATOGRAPHY

The monomer and the oligomers of a bioactive cyclic peptide were separ ated using micellar electrokinetic chromatography (MEKC) in order to d etermine if oligomeric forms of the peptide were present or not. Produ cing cyclic peptides involves the formation of an intramolecular disul phide bridge. During cyclisation, intermolecular disulphide bonds may be formed, thus resulting in unwanted oligomeric forms of the peptide. The cyclic peptide studied was shown by size-exclusion chromatography to be capable of forming a monomer, dimer, trimer and tetramer. The h igher resolution MEKC provides was needed to separate further componen ts of the oligomers. In phosphate buffer pH 7.5 containing sodium dode cyl sulphate 20 species could be separated in 18 min. Both linear and cyclic oligomeric isomers appeared to be present.