Applications of capillary zone electrophoresis to peptide mapping

Peptide mapping of proteins by capillary electromigration methods

This review article provides a wide overview of important developments and applications of capillary electromigration methods in the area of peptide mapping of proteins in the period 1997-mid-2022, including review articles on this topic. It deals with all major aspects of peptide mapping by capillary electromigration methods: i) precleavage sample preparation involving purification, preconcentration, denaturation, reduction and alkylation of protein(s) to be analyzed, ii) generation of peptide fragments by off-line or on-line enzymatic and/or chemical cleavage of protein(s), iii) postcleavage preparation of the generated peptide mixture for capillary electromigration separation, iv) separation of the complex peptide mixtures by one-, two- and multidimensional capillary electromigration methods coupled with mass spectrometry detection, and v) a large application of peptide mapping for variable purposes, such as qualitative analysis of monoclonal antibodies and other protein biopharmaceuticals, monitoring of posttranslational modifications, determination of primary structure and investigation of function of proteins in biochemical and clinical research, characterization of proteins of variable origin as well as for protein and peptide identification in proteomic and peptidomic studies.

Determination of acidity constants and ionic mobilities of polyprotic peptide hormones by CZE

CZE has been applied to determination of thermodynamic acidity constants (pKa ) of ionogenic groups and actual ionic mobilities of polyprotic peptides-synthetic human and salmon gonadotropin-releasing hormones and their derivatives and fragments. First, the mixed acidity constants, pKa,imix, of ionogenic groups, and actual ionic mobilities, mi , of gonadotropin-releasing hormone peptides were determined by nonlinear regression analysis of pH dependence of their effective electrophoretic mobilities. The effective mobilities were measured by CZE in a series of BGEs within a broad pH range (1.80-12.10), at constant ionic strength (25 mM) and reference temperature (25°C). Second, the pKa,imix values were recalculated to thermodynamic pKa s using the Debye-Hückel theory. Thermodynamic pKa of carboxyl groups was estimated to be in the range of 2.5-3.3 for C-terminal amino acids of the above peptides, and 5.2 for glutamic acid in the middle of peptide chain; pKa of imidazolyl group of histidine residues was in the range of 5.7-6.8, pKa of N-terminal amino group of the peptide with free N-terminus was equal to 6.2, pKa of phenol group of tyrosine residues was in the range of 9.8-10.8, and pKa of guanidinyl group or arginine residues reached values 11.1-11.3, depending on the position of the residues in the peptide and on the amino acid sequence of the peptide. Absolute values of actual ionic mobilities of peptides with charge number ±2 were in the range (14.6-18.6) × 10(-9) m(2) V(-1) s(-1) , and ionic mobilities of peptides with charge number ±1 reached values (6.5-12.9) × 10(-9) m(2) V(-1) s(-1) .

Improved capillary electrophoresis conditions for the separation of kinase substrates by the laser micropipet system

Phosphorylated and nonphosphorylated forms of peptide substrates for protein kinase C (PKC) and calcium-calmodulin activated kinase II (CamKII) were separated by capillary zone electrophoresis. Electrophoresis of the peptide substrates and products in biologic buffer solutions in uncoated capillaries yielded asymmetric analyte peaks with substantial peak tailing. Some of the peptides also exhibited broad peaks with unstable migration times. To improve the electrophoretic separation of the peptides, several strategies were implemented: extensive washing of the capillary with a base, adding betaine to the electrophoretic buffer, and coating the capillaries with polydimethylacrylamide (PDMA). Prolonged rinsing of the capillaries with a base substantially improved the migration time reproducibility and decreased peak tailing. Addition of betaine to the electrophoretic buffer enhanced both the migration time stability as well as the theoretical plate numbers of the peaks. Finally PDMA-coated capillaries brought about significant improvements in the resolving power of the separations. These modifications all utilized an electrophoretic buffer that was compatible with a living biologic cell. Consequently they should be adaptable for the new capillary electrophoresis-based methods to measure kinase activation in single cells.

Miniaturized ultrathin slab gel electrophoresis with thermal lens microscope detection and its application to fast genetic diagnosis

A miniaturized ultrathin slab gel electrophoresis (MUSGE) apparatus was developed, and fast separation of DNA fragments was obtained using it. To obtain sufficient separation efficiency in a limited space, a discontinuous buffer system was used. In general, it is difficult to cast a discontinuous ultrathin slab gel of adequate quality. However, the miniaturized resolving gel could be cast by taking advantage of the "capillary phenomenon" of the ultrathin channel. A gradient plate was used to control the height of the resolving gel and to form a clear interface between the concentrating gel and the resolving gel. This method was used to cast multiple gels simultaneously and reproducibly. The gradient plate also facilitated sample introduction, which was carried out by using a micropipet. A 25-mm-long and 80-micron thick-resolving gel was used to separate the 100-base pair ladder DNA within 10 min. Bandwidth was reduced to 100-200 microns, thus improving the number of theoretical plates to 22,000, which was comparable to that in conventional slab gel electrophoresis even though the migration distance was reduced to 1/10. Satisfactory lane-to-lane reproducibility (RSD < 1.0%, n = 6) and gel-to-gel reproducibility (RSD < 2.7%, n = 4) were obtained. Finally, the MUSGE apparatus was successfully applied to get a rapid genetic diagnosis.

Capillary electrophoresis of peptides

This article gives a review of the recent developments in capillary electrophoresis (CE) of peptides. New approaches to the theoretical description of electromigration behavior of peptides are described, and methodological aspects of CE separations of peptides such as selection of separation conditions, sample treatment, suppression of peptide adsorption to the capillary wall and specificities of CE separation modes are discussed. Progress in application of high performance detection schemes, namely laser-induced fluorescence and mass spectrometry, in peptide separations by CE is presented. Applications of different CE techniques, zone electrophoresis, isotachophoresis, isoelectric focusing, affinity electrophoresis, electrokinetic chromatography and electrochromatography to peptide analysis, preparation and physicochemical characterization are demonstrated.

Behavior of peptides in capillary electrophoresis: effect of peptide charge, mass and structure

In the last decade the large potential of capillary electrophoresis as a technique for separation and characterization of peptides has been demonstrated extensively. In this field, a large number of chemical structures has to be taken into consideration, for which very often no data or even standards are available. As a result, there has been a strong desire to relate electrophoretic behavior to molecular properties and structure of the compounds. The activities in that direction, in the area of capillary zone electrophoresis, are critically reviewed. Special attention is paid to peptide charge, mass, hydrophobicity and structure, and their influence on the selectivity of the separation. Also, some complexation phenomena are discussed.