Isotope-Coded Affinity Tagging Technique Using Avidin Functional Affinity Electrophoresis: An Alternative to an Avidin Affinity Column

Applications of Immobilized Metal Affinity Electrophoresis

Immobilized metal affinity electrophoresis (IMAEP) is a technique in which metal ions are integrated in a localized polyacrylamide gel section and which possess an insignificant electrophoretic migration. IMAEP has been implemented into both native and sodium dodecyl sulfate (SDS) one-dimensional (1-D) and two-dimensional (2-D) polyacrylamide gel electrophoresis (PAGE) systems. The gel piece containing metal ions is overlaid on top of an individual well in 1-D IMAEP, and gel strip is overlaid on top of the two-second dimensional polyacrylamide gel in 2-D IMAEP, respectively. This method is used to capture/enrich metal ion binding proteins. Due to the preferential binding between iron (III), manganese (II), or aluminum (III) ions and the phosphate group, these metal ions are used to capture/enrich phosphoproteins from a mixture of proteins. Data shows that SDS not only does not interfere with the extraction of phosphoproteins but also help unmasking phosphate groups by unfolding the phosphoproteins to facilitate metal ion-phosphate binding while supplying the protein with negative charges. In addition, IMAEP together with avidin functional affinity electrophoresis (AFAEP) and antibody affinity electrophoresis (AAEP) have been used to demonstrate the separation of proteins by their functionalities. AFAEP is used here to capture biotinylated proteins using avidin and AAEP is used here to capture protein G using IgG.

Capturing biotinylated proteins and peptides by avidin functional affinity electrophoresis

Avidin functional affinity electrophoresis (AFAEP) is a variational method of affinity electrophoresis. In this technique, avidin is immobilized within a small area of the gel matrix by interaction with acrylamide and/or polyacrylamide either directly or through bifunctional linker glutaraldehyde during polymerization. Analytes can be heated with Tris-glycine sodium dodecyl sulfate (SDS) sample buffer so that biotinylated peptides/proteins are negatively charged and migrate electrophoretically towards the cathode through the avidin zone regardless of their isoelectric point (pI) values. Alternatively, if the behavior of the biotinylated analytes is known, the SDS treatment is not required. The polarity of the electrodes is set such that biotinylated analytes migrate electrophoretically through the avidin zone. This technique can work with or without SDS in gel running buffer. The AFAEP method allows the capture and concentration of biotinylated peptides/proteins. The values of this technique stem from a combination of merits of polyacrylamide gel electrophoresis and affinity technology.