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pH‐Dependence of complexation constants and complex mobility in capillary electrophoresis separations of dipeptide enantiomers
Author(s) -
Sabbah Samir,
Süß Falko,
Scriba Gerhard K. E.
Publication year - 2001
Publication title -
electrophoresis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.666
H-Index - 158
eISSN - 1522-2683
pISSN - 0173-0835
DOI - 10.1002/1522-2683(200109)22:15<3163::aid-elps3163>3.0.co;2-a
Subject(s) - enantiomer , chemistry , dipeptide , cyclodextrin , capillary electrophoresis , beta cyclodextrins , stability constants of complexes , beta (programming language) , stereochemistry , peptide , chromatography , organic chemistry , aqueous solution , biochemistry , computer science , programming language
The chiral separation of the LL ‐ and DD ‐enantiomers of the dipeptides Ala‐Tyr, Phe‐Phe, and Asp‐PheOMe has been investigated at pH 2.5 and pH 3.5 using β‐cyclodextrin (β‐CD), heptakis‐(2,6‐di‐ O ‐methyl)‐β‐cyclodextrin, and heptakis‐(2,3,6‐tri‐ O ‐methyl)‐β‐cyclodextrin as chiral selectors. According to elecrospray massspectrometry, heptakis‐(2,6‐di‐ O ‐methyl)‐β‐cyclodextrin was a mixture of six isomers. Reversal of the enantiomer migration order upon increasing the buffer pH from 2.5 to 3.5 was observed for all peptides with β‐cyclodextrin, for Ala‐Tyr and Phe‐Phe in the presence of heptakis‐(2,3,6‐tri‐O‐methyl)‐β‐cyclodextrin, and for Ala‐Tyrusing heptakis‐(2,6‐di‐O‐methyl)‐β‐cyclodextrin. The migrationbehavior could be explained on the basis of the complexationconstants and the mobilities of the peptide‐cyclodextrincomplexes. Both, the binding constants and complex mobilities decreased with increasing pH as the overall‐charge of the peptides decreased. While the complexation constants primarily determined the migration order at pH 2.5, complex mobility dominated inmost cases at pH 3.5.