Determination of enantiomers in a synthetic argininal peptide using capillary zone electrophoresis and high-performance liquid chromatography

Enantioseparation of cis and trans nucleosides, aromatic analogues of stavudine, by capillary electrophoresis and high-performance liquid chromatography

Compounds 1-4 are diastereoisomeric thymine derivatives of isochroman aromatic analogues of stavudine, an approved drug. Both capillary electrophoresis (CE) and high-performance liquid chromatography (HPLC) techniques were used to separate these species with high resolution and thus permit the determination of enantiomeric excess. Chiral selectivity was developed using anionic (highly sulfated) cyclodextrins as chiral selectors in CE and amylose, cellulose and cyclodextrin chiral stationary phases by HPLC. The HPLC method was found to be more efficient than the CE method and was applied, after validation (repeatability, limit of detection, limit of quantification) to follow and quantify the kinetics of a stereoselective esterification.

Enantioseparation of four cis and trans diastereomers of 2′,3′-didehydro-2′,3′-dideoxythymidine analogs, by high-performance liquid chromatography and capillary electrophoresis

Compounds 1-4 are the four stereoisomers of a synthetic new potential antiviral agent (d4T analog) containing two chiral centers and a base (uracil). Both high-performance liquid chromatography (HPLC) and capillary electrophoresis (CE) techniques were used to separate and quantify enantiomers with high resolution. The determination of enantiomeric purity of the compounds was developed using both amylose chiral stationary phase by HPLC and anionic cyclodextrins (highly S-CD) as chiral selectors in CE. The HPLC method was found to be superior in sensitivity to the CE method.

Recent advances in capillary electrophoresis of peptides

The article gives a comprehensive review on the recent developments in the applications of high-performance capillary electromigration methods, including zone electrophoresis, isotachophoresis, isoelectric focusing, affinity electrophoresis, electrokinetic chromatography and electrochromatography, to analysis, preparation and physicochemical characterization of peptides. The article presents new approaches to the theoretical description and experimental verification of electromigration behavior of peptides, and covers the methodological aspects of capillary electroseparations of peptides, such as strategy and rules for the rational selection of separation mode and experimental conditions, sample treatment, suppression of peptide adsorption to the inner capillary wall, new developments in individual separation modes and new designs of detection systems. Several types of applications of capillary electromigration methods to peptide analysis are presented: conventional qualitative and quantitative analysis for determination of purity, determination in biomatrices, monitoring of physical and chemical changes and enzymatic conversions, amino acid and sequence analysis and peptide mapping of proteins. Some examples of micropreparative peptide separations are given and capabilities of capillary electromigration techniques to provide important physicochemical characteristics of peptides are demonstrated.

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

The separation of dipeptide and tripeptide enantiomers using negatively charged single isomers as well as randomly sulfated and sulfonated cyclodextrins (CDs) was investigated with respect to the amino acid sequence of the peptides and the nature of the CDs. Standardized conditions concerning buffer pH and molarity, CD concentration, and separation voltage were applied. Compared to suffobutylether-beta-CD and heptakis-(2,3-dimethyl-6-sulfato)-beta-CD, randomly sulfated beta-CD as well as the single isomer derivatives heptakis-6-sulfato-beta-CD and heptakis-(2,3-diacetyl-6-sulfato)-beta-CD were the more universal CDs for enantioseparations. The enantiomer migration order depended to a greater extent on the CD than on the amino acid sequence of the peptide although small structural differences such as formation of a peptide amide or ester affected the chiral recognition by the randomly 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 DD, was observed when heptakis-6-sulfato-beta-CD was applied as chiral selector.