Size separation of proteins by capillary zone electrophoresis with cationic hitchhiking

A comparative study of CE-SDS, SDS-PAGE, and Simple Western-Precision, repeatability, and apparent molecular mass shifts by glycosylation

SDS gel electrophoresis is a commonly used approach for monitoring purity and apparent molecular mass (Mr) of proteins, especially in the field of quality control of biopharmaceutical proteins. The technological installation of CE-SDS as the replacement of the slab gel technique (SDS-PAGE) is still in progress, leading to a continuous improvement of CE-SDS instruments. Various CE-SDS instruments, namely Maurice (CE-SDS/CE-SDS PLUS) and Wes by ProteinSimple as well as the microchip gel electrophoresis system LabChip® GXII Touch™ HT by PerkinElmer were tested for precision and repeatability compared to SDS-PAGE (Bio-Rad). For assessing these quality control parameters, standard model proteins with minor post-translational modifications were used. Overall, it can be concluded that the CE-SDS-based methods are similar to SDS-PAGE with respect to these parameters. Quality characteristics of test systems gain more significance by testing proteins that do not behave like model proteins. Therefore, glycosylated proteins were analyzed to comparatively investigate the influence of glycosylation on Mr determination in the different instruments. In some cases, high deviations were found both among the methods and with regard to reference values. This article provides possible explanations for these findings.

Microparticle Delivery of Protein Markers for Single-Cell Western Blotting from Microwells

Immunoblotting confers protein identification specificity beyond that of immunoassays by prepending protein electrophoresis (sizing) to immunoprobing. To accurately size protein targets, sample analysis includes concurrent analysis of protein markers with known molecular masses. To incorporate protein markers in single-cell western blotting, microwells are used to isolate individual cells and protein marker-coated microparticles. A magnetic field directs protein-coated microparticles to >75% of microwells, so as to 1) deliver a quantum of protein marker to each cell-laden microwell and 2) synchronize protein marker solubilization with cell lysis. Nickel-coated microparticles are designed, fabricated, and characterized, each conjugated with a mixture of histidine-tagged proteins (42.3-100 kDa). Imidazole in the cell lysis buffer solubilizes protein markers during a 30 s cell lysis step, with an observed protein marker release half-life of 4.46 s. Across hundreds of individual microwells and different microdevices, robust log-linear regression fits (R2 > 0.97) of protein molecular mass and electrophoretic mobility are observed. The protein marker and microparticle system is applied to determine the molecular masses of five endogenous proteins in breast cancer cells (GAPDH, β-TUB, CK8, STAT3, ER-α), with <20% mass error. Microparticle-delivered protein standards underpin robust, reproducible electrophoretic cytometry that complements single-cell genomics and transcriptomics.

Determination of the stereoisomers in aqueous medium and serum and validation studies of racemic aminoalkanol derivatives of 1,7-dimethyl-8,9-diphenyl-4-azatricyclo[5.2.1.0(2,6) ]dec-8-ene-3,5,10-trione, potential new anticancer drugs, by capillary electrophoresis

A new method for the determination of the stereoisomers, in aqueous medium and serum, of the racemic aminoalkanol derivatives I and II of 1,7-dimethyl-8,9-diphenyl-4-azatricyclo[5.2.1.0(2,6) ]dec-8-ene-3,5,10-trione, which were found in earlier studies to be potential anticancer drugs, was developed and validated. The optimized conditions included 25 mM phosphate buffer adjusted to pH 2.5, containing γ-cyclodextrin at a concentration of 5% m/v, as background electrolyte, an applied voltage of +10 kV, and a temperature of 25°C. Separations were carried out using a fused-silica capillary. The developed method of determining the enantiomers of compounds I(S), I(R) and II(S), II(R) was characterized by the following parameters: a detection time within 10.8 min, a detection limit in the range of 141.2-141.7 ng/mL using the UV absorption detection at 200 nm. Good linearity (R(2) = 0.9989-0.9998) was achieved within the range of concentrations studied. A very good extraction yield of 95.4-99.7% was achieved, and recoveries were carried out from both aqueous solutions and matrix serum. The repeatability of the method for peak areas with an accuracy of the determined concentrations of the analytes in the range of 1.43-1.89%, and limits of quantitation in the range of 432.4-436.3 ng/mL were achieved.

Recent developments in capillary and microchip electroseparations of peptides (2011-2013)

The review presents a comprehensive survey of recent developments and applications of capillary and microchip electroseparation methods (zone electrophoresis, ITP, IEF, affinity electrophoresis, EKC, and electrochromatography) for analysis, isolation, purification, and physicochemical and biochemical characterization of peptides. Advances in the investigation of electromigration properties of peptides, in the methodology of their analysis, including sample preseparation, preconcentration and derivatization, adsorption suppression and EOF control, as well as in detection of peptides, are presented. New developments in particular CE and CEC modes are reported and several types of their applications to peptide analysis are described: conventional qualitative and quantitative analysis, determination in complex (bio)matrices, monitoring of chemical and enzymatical reactions and physical changes, amino acid, sequence and chiral analysis, and peptide mapping of proteins. Some micropreparative peptide separations are shown and capabilities of CE and CEC techniques to provide relevant physicochemical characteristics of peptides are demonstrated.