Electrophoresis slab-gel

Fignre 6-12. Slab gel apparatus. The glass plates are shown assembled with the side and bottom spacers in place and the comb inserted at the notch. [From F. W. Studier, J. Mol. Biol., 79 237 (1973).] 

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There are several forms of electrophoresis. In slab gel electrophoresis the conducting buffer is retained within a porous gel of agarose or polyacrylamide. Slabs are formed by pouring the gel between two glass plates separated by spacers. Typical thicknesses are 0.25-1 mm. Gel electrophoresis is an important technique in biochemistry, in which it is frequently used for DNA sequencing. Although it is a powerful tool for the qualitative analysis of complex mixtures, it is less useful for quantitative work. 

The STR data generated at NIST were based on amplifying i.o ng of the genomic DNA with fluorescent labelled primers. The PCR amplified products were analyzed by slab gel electrophoresis followed by imaging with a Molecular Dynamics Fluorl-mager 595 or by capUlary electrophoresis using a PE-ABI 310 Genetic Analyzer. 

Originally, polyacrylamide was used as an anticonvective additive in slab gel electrophoresis,79 but later its molecular sieving capability was also utilized.80 Polyacrylamide is a polymer built exclusively from monomeric units, with or without cross linking.81 A chemically cross-linked network is... 

Guttman, A. and Nolan, J., Comparison of the separation of proteins by sodium dodecyl sulfate-slab gel electrophoresis and capillary sodium dodecyl sulfate-gel electrophoresis, Anal. Biochem., 221, 285, 1994. 

The method of Kato and Nakai (27) for determining protein surface hydrophobicity was adapted for evaluating procyanidin binding to BSA and Gl. The procedure is based on the fact that the fluorescence quantum yield of cis-parinaric acid increases 40-fold when cis-parinaric acid enters a hydrophobic environment from a hydrophilic environment. The digestion of BSA by trypsin in the presence of procyanidin dimer, procyanidin trimer and black bean procyanidin polymer was evaluated by discontinuous sodium dodecyl sulfate (SDS) slab gel electrophoresis and a picryl sulfonic acid (TNBS) assay (28). 

CE provides analysis based on orthogonal separation principles compared to other techniques as well as high resolving power. Like slab gel electrophoresis, CE is a family of techniques that resolve sample components by differences in intrinsic molecular characteristics such as size, mass, charge, differential interaction, and isoelectric point (pi). 

A schematic representation of a CE system is presented in Figure 9.1. In this diagram, the CE components have obvious counterparts to those found in slab gel electrophoresis. Instead of buffer tanks there are two small buffer reservoirs, and the capillary takes the place of the gel (or more accurately, a gel lane). The capillary is immersed in the electrolyte-filled reservoirs, which also make contact with the electrodes connected to a high-voltage power supply. A new feature to the conventional gel electrophoresis format is the presence of an online detection system. 

Size-based analysis of SDS-protein complexes in polyacrylamide gels (SDS-PAGE) is the most common type of slab gel electrophoresis for the characterization of polypeptides, and SDS-PAGE is one of the most commonly used methods for the determination of protein molecular masses.117 The uses for size-based techniques include purity determination, molecular size estimation, and identification of posttranslational modifications.118119 Some native protein studies also benefit from size-based separation, e.g., detection of physically interacting oligomers. 

Based on its nature (aqueous solutions, physiological conditions, well-investigated labeling, and staining reactions) and the historical transition from slab-gel electrophoresis to CE, the main targets are biological and bioequivalent samples such as proteins, peptides, polynucleotides, oligonucleotides, and carbohydrates. 

FIGURE 3.2 A slab gel electrophoresis apparatus. A voltage source generates an electric potential difference between the upper and lower buffer chambers, causing the applied DNA sample to migrate through the gel toward the positive electrode. 

Vertical slab-gel electrophoresis system that allows exact and constant temperation of the gel through circulation of temperated buffer around both sides of the gel. Specialised systems are available from several companies. 

An apparatus for horizontal slab gel electrophoresis. Courtesy of Hoefer Pharmacia Biotech Inc., San Francisco. 

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