Cyclodextrin aided separation of peptides and proteins by capillary zone electrophoresis

Carboxymethylated-beta-cyclodextrin (CMBCD) in the electrophoretic medium (aqueous 50 mM sodium phosphate, pH 2.5) enhanced the separation using raw fused-silica capillaries in CZE of the four standard proteins: alpha-chymotrypsinogen A, cytochrome c, lysozyme and ribonuclease A. Furthermore, with 20 mM CMBCD in the electrophoretic medium, the cis-trans isomers of angiotensin could be separated at room temperature, whereas the separation of the conformers required subambient temperatures as low as -20 degrees C without CMBCD in the electrophoretic medium [50 mM sodium phosphate (pH 2.5), containing 10% (v/v) methanol]. Addition of heptakis(2,6-di-O-methyl)-beta-cyclodextrin (DMBCD) had no effect on the separation of the above proteins and peptides. The results suggest that in microcolumn separation techniques, certain cyclodextrin additives can be useful selectivity enhancers.