Sodium dodecyl sulfate-gel electrophoresis of proteins employing short capillaries

Implication of the differential roles of metallothionein 1 and 2 isoforms in the liver of rats as determined by polyacrylamide-coated capillary zone electrophoresis

Metallothioneins (MTs), determined by polyacrylamide-coated capillary zone electrophoresis (CZE), coincided well with those described by enzyme-linked immunosorbent assay. By using CZE, MT isoforms 1 (MT-1) and 2 (MT-2) were well separated and determined in the liver cytosol of LEC rats and Wistar rats administered CdCl(2). The total concentrations of MTs in the liver cytosol of LEC rats increased age-dependently as 1.0, 2.1, and 7.2mg/g wet weight of the liver at the age of 5, 10, and 15 weeks, respectively, and those of Wistar rats that had received daily CdCl(2) also increased with time of CdCl(2) as 0.5 and 1.2mg/g wet weight of the liver for 3 and 6 consecutive administration days, respectively. The MT-1/MT-2 ratio in the liver cytosol of LEC rats decreased age-dependently as 1.75, 1.49, and 0.76 at the age of 5, 10, and 15 weeks, respectively. In contrast, that of Wistar rats increased with time of exposure to the metal ion CdCl(2) as 1.1 and 1.6 for 3 and 6 administration days, respectively. Copper accumulation in the liver of LEC rats has already been reported. The present results indicated that the mechanism of the induction of MT synthesis differs between LEC rats, who lack ATP7B, and Wistar rats, who were given a toxic metal ion. On the basis of these results, we propose that MT-1 is related to the metabolism or detoxification of toxic metals such as Cd, and in contrast, MT-2 is responsible for the homeostasis of essential metals such as Cu.

Combination of electrophoretic techniques for comprehensive analysis of complex protein systems

Analysis of proteins in complex mixtures such as cell lysates is presently performed by two-dimensional polyacrylamide gel electrophoresis under denaturing conditions (denaturing 2-D PAGE) followed by extraction of proteins from gel pieces and structural analysis of the proteins. This type of protein analysis is contributing to the correlation of information stored in DNA sequences with the structure of the product polypeptides. However, denaturing 2-D PAGE has its own limitations and it is necessary to develop various methods of protein analysis to reconstruct the total structure and function of proteins in complex systems. This review article summarizes the work in our laboratory to explore proteins in human plasma combining various electrophoretic techniques: nondenaturing and denaturing 2-D PAGE, capillary electrophoresis, and agarose gel isoelectric focusing.

On-line coupling of high performance gel filtration chromatography with imaged capillary isoelectric focusing using a membrane interface

A high performance liquid chromatography system, a sample preparation device, and an imaged capillary IEF (CIEF) instrument are integrated and multiplexed on-line. The system is equivalent to two-dimensional polyacrylamide gel electrophoresis (2-D PAGE), by transferring the principle of 2-D separation to the capillary format. High performance liquid chromatography (HPLC) provides protein separation based on size using a gel filtration chromatography (GFC) column. Each eluted protein is sampled and directed to a novel microdialysis hollow fiber membrane device, where simultaneous desalting and carrier ampholyte mixing occurs. The sample is then driven to the separation column in an on-line fashion, where CIEF takes place. The fluidic technology used by our 2-D system leads to natural automation. The coupling of the two techniques is simple. This is attributed to high speed and efficiency of the sample preparation device that acts as an interface between the two systems, as well as the speed and simplicity of our whole column absorption imaged CIEF instrument. To demonstrate the feasibility of this approach, the separation of a mixture of two model proteins is studied. Sample preparation and CIEF were complete in just 4-5 min, for each of the eluted proteins. Total analysis time is about 24 min. Three-dimensional data representations are constructed. Challenges and methods to further improve our instrument are discussed, and the design of an improved horseshoe-shaped sample preparation sample loop membrane interface is presented and characterized.

Electrokinetic injection in capillary electrophoresis and its application to the analysis of inorganic compounds

In capillary electrophoresis, electrokinetic injection is a highly controversial sampling technique. It is a simple mode of sample introduction which is suitable for on-line preconcentration of the analytes, but its precision and accuracy are more strongly affected by experimental conditions compared to hydrodynamic injection. In the first part of this paper the features of electrokinetic and hydrodynamic injections are compared, followed by a detailed discussion on the different biases of electrokinetic injection and on how to reduce them. Finally, applications of the electrokinetic injection are reviewed with special emphasis on the analysis of inorganic compounds.

Size separation of sodium dodecyl sulfate complexes of human plasma proteins by capillary electrophoresis employing linear polyacrylamide as a sieving polymer

Electrophoretic conditions to separate sodium dodecyl sulfate (SDS) complexes of human plasma proteins according to their size differences, by capillary electrophoresis employing linear polyacrylamide as a sieving matrix (LPA-CE), have been examined. Using the optimized separation conditions, SDS complexes of human plasma proteins not treated with reducing agents were separated into about 40 peaks and shoulders within 60 min. The molecular mass values of major peaks in a separation pattern were estimated from a plot of molecular mass and migration time for standard proteins and some of the major plasma proteins have been identified on the pattern. The electrophoretic conditions were successfully applied for the analysis of proteins in immunoglobulin G (IgG) myeloma sera.

Correlation of plasma protein separation patterns obtained by two-dimensional polyacrylamide gel electrophoresis and by capillary electrophoresis

We used three different electrophoretic techniques for the analysis of human plasma proteins: (i) two-dimensional polyacrylamide gel electrophoresis (2-D PAGE), with sodium dodecyl sulfate (SDS) used only in slab gel electrophoresis; (ii) capillary isoelectric focusing (CIEF) with no denaturants; (iii) linear polyacrylamide (LPA)-filled capillary electrophoresis with SDS (SDS-CE). With technique (i), data on isoelectric point and molecular size of plasma proteins can be obtained. Techniques (ii) and (iii) are suited to obtain quantitative information on proteins. The separation principle used in technique (ii) is closely related to that used in the first dimension of technique (i), and that used in technique (iii) related to that in the second dimension of technique (i). Therefore, we could successfully correlate protein separation patterns obtained by 2-D PAGE and those obtained by capillary electrophoresis. The advantages of correlating data obtained by various electrophoretic techniques in the course of constructing a comprehensive database on human plasma proteins are discussed.

Capillary electrophoresis in presence of sodium dodecyl sulfate and a sieving medium

For analysis of proteins in presence of sodium dodecyl sulfate (SDS), basic knowledge about their behavior in presence and absence of sieving medium is required. Capillary electrophoresis (CE) is particularly suitable for this purpose. Although various polymers are used as sieves in CE analysis in presence of SDS, attention must be paid to possible interaction between SDS and the polymer. For obtaining new insights polymers with defined molecular weight and distribution should be utilized.

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.

Capillary electrophoresis procedures for serum protein analysis: comparison with established techniques

Methods using automated capillary electrophoresis (CE) instrumentation are available for serum protein electrophoresis with monoclonal band quantitation, isoelectric focusing and sodium dodecyl sulphate-polyacrylamide gel electrophoresis separations. The advantages of CE over previous gel methods relate to the time and labour saved by the automated instrumentation. High pI monoclonal bands and cryoglobulin specimens can be successfully analysed by CE. However, if the CE application uses a standard company supplied kit, then the cost savings are often negated by the high cost of the kit. Improvements such as the inclusion of both a UV-Vis as well as a fluorescence detector as standard within the one commercial instrument, the production of coated IEF capillaries with a useful life of at least 100 samples, and the introduction of a capillary array into all commercial instrumentation would ensure greater use of CE within both the clinical and other protein laboratories.

Effects of catholytes on the mobilization of proteins after capillary isoelectric focusing

Purified proteins and human plasma proteins were separated by capillary isoelectric focusing and detected by cathodic mobilization, e.g. by replacing the cathodic sodium hydroxide solution by solutions containing another anion. The effect of catholyte anions on the resolution of mobilized proteins was examined. Compared with the chloride or phosphate anion, organic anions having small dissociation constants improved protein resolution, especially in the range of acidic proteins. Among the catholytes examined, acetic acid gave the best resolution for purified proteins and human plasma proteins. Measurement of the changes of electric current during the mobilization process indicated that organic anions with low mobility move slowly towards the anode and retard changes of pH gradient in the capillary. Isoelectric focusing, cathodic mobilization, and direct pH measurement in polyacrylamide gel columns (1.3 mm internal diameter and 38 mm long) also revealed these effects of low mobility anions. In order to visualize the behavior of human plasma proteins in the mobilization step, micro two-dimensional polyacrylamide gel electrophoresis was employed. The results indicated that the proteins migrate towards the cathode, preserving their relative positions attained during the isoelectric focusing step.