Effect of temperature and viscosity of sieving medium on electrophoretic behavior of sodium dodecyl sulfate-proteins on capillary electrophoresis in presence of pullulan

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.

High-Resolution capillary electrophoresis separation of large RNA under non-aqueous conditions

Large RNAs including messenger RNAs (mRNAs) are promising candidates for development of new drug products and vaccines. Development of high resolution methods for direct analysis of large RNAs, especially for purity in general and size or length in particular, is critical to support new drug development and manufacture. However, resolution based on size or length for large RNAs is limited even by capillary electrophoresis (CE), which is one of the most efficient separation methods for nucleic acids in general. This paper presents a capillary gel electrophoresis (CGE) method for separating large RNA molecules by size or length under strongly denaturing, non-aqueous conditions. We believe that our work constitutes the first time that a gel suitable for CGE prepared with high molecular weight polymers and using only formamide as solvent has been successfully employed to analyze large RNAs on the basis of their size or length with high resolution. With an eye toward application for mRNAs in particular, separation conditions in this work were optimized for RNAs approximately 2000 nucleotides (nt) in length. As compared to a standard CGE method using an aqueous gel, resolution for commercially-available RNA ladder components at 1500 and 2000 nt is increased approximately 6-fold. The impacts of polymer type, molecular weight of the polymer, and polymer concentration on the separation were studied and optimized. Analysis of the results presented here also provides guidance for optimization of separation conditions for RNAs with different sizes as needed for particular applications in the future.

Protein separation by capillary gel electrophoresis: a review

Capillary gel electrophoresis (CGE) has been used for protein separation for more than two decades. Due to the technology advancement, current CGE methods are becoming more and more robust and reliable for protein analysis, and some of the methods have been routinely used for the analysis of protein-based pharmaceuticals and quality controls. In light of this progress, we survey 147 papers related to CGE separations of proteins and present an overview of this technology. We first introduce briefly the early development of CGE. We then review the methodology, in which we specifically describe the matrices, coatings, and detection strategies used in CGE. CGE using microfabricated channels and incorporation of CGE with two-dimensional protein separations are also discussed in this section. We finally present a few representative applications of CGE for separating proteins in real-world samples.

Size separation of proteins by capillary zone electrophoresis with cationic hitchhiking

The paper describes a method of size separation of proteins by capillary sieving electrophoresis with cationic surfactant. Proteins are separated within 12 min with repeatability of migration times better than 0.2%. Some proteins achieve the separation efficiency of 200,000 theoretical plates. The method can be used for determination of protein relative molecular masses. The accuracy of the determined relative molecular masses and the limitation of the method were investigated by the analysis of more than 60 proteins. The method also allows separation of protein oligomers. Proteins can be quantitated after the electrokinetic injection in the concentration range 0.07-0.43 g/L. The average detection limit is about 2 mg/L.

Chemical modification of proteins to improve the accuracy of their relative molecular mass determination by electrophoresis

We studied the electrophoretic behavior of basic proteins (cytochrome c and histone III) and developed a carbamylation method that normalizes their electrophoretic size separation and improves the accuracy of their relative molecular mass determined electrophoretically. In capillary zone electrophoresis with cationic hitchhiking, native cytochrome c does not sufficiently bind cationic surfactants due to electrostatic repulsion between the basic protein and cationic surfactant. Carbamylation suppresses the strong positive charge of the basic proteins and results in more accurate relative molecular masses.

On the use of the activation energy concept to investigate analyte and network deformations in entangled polymer solution capillary electrophoresis of synthetic polyelectrolytes

The activation energy associated with the electrophoretic migration of an analyte under given electrolyte conditions can be accessed through the determination of the analyte electrophoretic mobility at various temperatures. In the case of the electrophoretic separation of polyelectrolytes in the presence of an entangled polymer network, activation energy can be regarded as the energy needed by the analyte to overcome the obstacles created by the separating network. Any deformation undergone by the analyte or the network is expected to induce a decrease in the activation energy. In this work, the electrophoretic mobilities of poly(styrenesulfonates) (PSSs) of various molecular weights (Mr 16 x 10(3) to 990 x 10(3)) were determined in entangled polyethylene oxide (PEO) solutions as a function of temperature (in the 17-60 degrees C range) and the PSS activation energies were calculated. The influences of the PSS molecular weight, blob sizes zetab of the separating network (related to the PEO concentration), ionic strength of the electrolyte and electric field strength (75-600 V/cm) were investigated. The results were interpreted in terms of analyte and network deformations and were confronted with those previously obtained for DNA migration in polymer solutions and chemical gels. For a radius of gyration Rg<zetab the activation energy increases with the PSS molecular mass, while the reverse is true for Rg>zetab, suggesting PSS and network deformations in the latter case. Increasing ionic strength resulted in an increase in the PSS activation energy, because of the decrease of their radii of gyration, which makes them less deformable. Finally, the activation energies of all the PSSs are a decreasing function of field strength and at high field strength tend to reach a constant value close to that for a small molecule.

Separation of proteins by sodium dodecylsulfate capillary electrophoresis in hydroxypropylcellulose sieving matrix with laser-induced fluorescence detection

Sodium dodecyl sulfate capillary electrophoresis by using hydroxypropylcellulose as the sieving matrix was developed for separation of proteins. 3-(2-furoyl)quinoline-2-carboxaldehyde, a fluorogenic dye, was used as the pre-column reagent to label proteins, which allows the use of laser-induced fluorescence to improve the detection sensitivity. Five standard proteins within the molecular mass range of 14,000-97,000 were used to test this method and a calibration curve was obtained between the molecular mass of these proteins and their peak migration times. This method was also applied to the separation of proteins from HT29 human colon adenocarcinoma cell extracts, and, typically, nearly 30 protein components could be resolved in a 20-min separation. Similar separation patterns were observed for the cell extract proteins when three running buffer systems were employed, indicating that buffer composition did not have much influence on the separation based on HPC sieving.

Capillary zone electrophoresis of proteins

This review article with 237 references is focused on capillary zone electrophoresis (CZE) of proteins. It includes discussion of modeling electrophoretic migration of proteins, sample pretreatment before the analysis, methods reducing the sorptions of proteins on the capillary wall, and techniques for increasing selectivity by using electrolyte additives including the sieving matrices. Significant progress in detection techniques, namely in laser-induced fluorescence and mass spectrometry, is emphasized. Modifications of CZE using specific interactions, such as affinity capillary electrophoresis or capillary immunoelectrophoresis, are debated as well as combination of CZE with other separation methods such as high performance liquid chromatography (HPLC). A number of practical applications of CZE of proteins are described.

Buffer additives other than the surfactant sodium dodecyl sulfate for protein separations by capillary electrophoresis

The different compounds utilized as additives to the electrolyte solutions employed in protein capillary zone electrophoresis (CZE) for minimizing protein-capillary wall interactions, for improving selectivity and resolution and for controlling the electroosmotic flow are reviewed. The dependence of the electroosmotic flow on the different variables that can be affected by the incorporation of an additive into the electrolytic solution is discussed. A list of the most effective additives employed for protein separations by CZE is reported in Appendix A.

Separation mechanism of pullulan solution-filled capillary electrophoresis of sodium dodecyl sulfate-proteins

The separation mechanism of capillary electrophoresis of sodium dodecyl sulfate (SDS)-proteins using pullulan with a molecular mass range of 50,000-100,000 as a separation matrix was investigated. The pullulan solution was filled into fused-silica capillaries whose inner walls were coated with linear polyacrylamide through chemically stable Si-C linkages. Baseline separations of SDS proteins were achieved at concentrations ranging from 3-10% w/v of pullulan. The entanglement threshold of pullulan solution was found to be around 0.5% w/v, indicating migration of SDS-proteins through an entangled pullulan network. Ferguson plots exhibited a linear relationship between log mobility and pullulan concentration. Linear relationships were also obtained for double logarithmic plots of the electrophoretic mobility and protein molecular mass. These results show that the separation is based on mass discrimination in accordance with the Ogston theory.