Electrophoretic stereoisomer separation of aspartyl dipeptides and tripeptides in untreated fused-silica and polyacrylamide-coated capillaries using charged cyclodextrins

The separation of diastereomeric and enantiomeric aspartyl model dipeptides and tripeptides including the isomeric iso-Asp containing beta-peptides was studied in untreated fused-silica capillaries and polyacrylamide-coated capillaries by capillary electrophoresis using negatively charged cyclodextrins as chiral selectors. While most diastereomers could be separated in the acidic pH range two dipeptide diastereomers were also resolved at alkaline pH. The separation of the enantiomers using carboxymethyl-beta-cyclodextrin or sulfobutyl-beta-cyclodextrins could be performed either between pH 2 and 3 when the peptides are positively charged or at pH 5.25 where the peptides migrate as uncharged compounds with the electroosmotic flow. Exploiting the self-mobility of the negatively charged cyclodextrins and reversing the polarity of the applied voltage, a reversal of the migration order of the enantiomers was achieved in polyacrylamide-coated capillaries. (C) 1998 Elsevier Science B.V. All rights reserved.