Influence of the amino acid sequence and nature of the cyclodextrin on theseparation of small peptide enantiomers by capillary electrophoresis usingrandomly substituted and single isomer sulfated and sulfonated cyclodextrins

The separation of dipepticle and tripeptide enantiomers using negatively ch arged single isomers as well as randomly sulfated and sulfonated cyclodextr ins (CDs) was investigated with respect to the amino acid sequence of the p eptides and the nature of the CDs. Standardized conditions concerning buffe r pH and molarity, CD concentration, and separation voltage were applied. C ompared to sulfobutylether-beta -CD and heptakis-(2,3-dimethyl-6-sulfato)-b eta -CD, randomly sulfated beta -CD as well as the single isomer derivative s heptakis-6-sulfato-beta -CD and heptakis-(2,3-diacetyl-6-suffato)-beta -C D were the more universal CDs for enantioseparations. The enantiomer migrat ion order depended to a greater extent on the CD than on the amino acid seq uence of the peptide although small structural differences such as formatio n of a peptide amide or ester affected the chiral recognition by the random ly substituted CD derivatives. Using sulfobutylether-beta -CD or heptakis-( 2,3-diacetyl-6-sulfato)-beta -CD the DD enantiomers migrated before the LL enantiomers; for most peptides while the opposite migration order, i.e. LL before DID, was observed when heptakis-6-sulfato-beta -CD was applied as ch iral selector.