Micellar electrokinetic chromatography separations of dynorphin peptide analogs

Prodynorphin is a precursor that has multiple cleavage sites to release various dynorphin opioid peptides. The dynorphin analogs used in this study have 18 amino acid residues. A series of dynorphin-like peptides, differing by a single residue (alanine substitution) were assembled by Fmoc solid-phase procedures and purified by preparative high performance liquid chromatography (HPLC). Separation of the Ala-scan dynorphin analogs was investigated by micellar electrokinetic chromatography (MEKC) employing anionic, cationic and zwitterionic surfactants. The role of electrostatic and hydrophobic forces in analyte-surfactant interactions is discussed with respect to the observed elution patterns. Separation of all dynorphin analogs by MEKC using a zwitterionic surfactant shows this technique to be powerful for separating closely related peptide species. It also demonstrates the potential for using MEKC for the prescreening of peptide libraries to determine their biological activity toward specific receptors. Results from the separation of dynorphin analogs by free solution and ion-pairing capillary electrophoresis are also presented.