Resolution of cis and trans isomers of peptides containing proline using capillary zone electrophoresis.

Capillary zone electrophoresis (CZE) is known for its high separation efficiency. Optically gated CZE is a form of CZE that allows rapid analyses while high separation efficiency is maintained. Analysis of peptides containing proline with CZE and optically gated CZE gives two peaks for dipeptides and multiple peaks for oligopeptides containing more than one proline. The multiple peaks are believed to be due to the cis and trans forms possible in peptide bonds containing proline. Isomerization between the cis and trans forms takes place at room temperature with a lifetime of seconds to minutes. Resolution of these peaks in CZE is found to be a function of separation efficiency and time of analysis. Rapid analyses with relatively lower separation efficiency give resolution equal to or better than that of longer analyses with much higher efficiency. This confirms the relationship between the multiple peaks and isomerization between the cis and trans forms. To extract kinetic information from the experimental data, a digital simulation is used to model the separation obtained experimentally. The equilibrium constant and rate constants that give the best fit of the simulated data to the experimental data are considered estimates of the actual values for the given experimental conditions.