Overview of Digital Electrophoresis Analysis

Overview of Digital Electrophoresis Analysis

Digital imaging is the method of choice for documentation and analysis of electrophoretic separations of protein and DNA. Digital images of gel electropherograms can be obtained rapidly using sCMOS and CCD-based cameras, and the images can be easily archived and analyzed using image analysis software. This overview defines important key terms and calculations for imaging, explains the capture process, reviews the range of technologies used for image capture, and provides an introduction to the software and methods used for one- and two-dimensional digital image analysis. © 2023 Wiley Periodicals LLC.

Immunoblotting and Immunodetection

Immunoblotting (western blotting) is used to identify specific antigens recognized by polyclonal or monoclonal antibodies. This unit provides protocols for all steps, starting with solubilization of the protein samples, usually by means of SDS and reducing agents. Following solubilization, the material is separated by SDS-PAGE and the antigens are electrophoretically transferred to a membrane, a process that can be monitored by reversible staining with Ponceau S. The transferred proteins are bound to the surface of the membrane, providing access to immunodetection reagents. After nonspecific binding sites are blocked, the membrane is probed with the primary antibody and washed. The antibody-antigen complexes are tagged with fluorophores, horseradish peroxidase, or alkaline phosphatase coupled to a secondary anti-IgG antibody, and detected using appropriate fluorescent imaging technologies or with chromogenic or luminescent substrates. Finally, membranes may be stripped and reprobed. © 2017 by John Wiley & Sons, Inc.

Immunoblotting and Immunodetection

Immunoblotting (western blotting) is used to identify specific antigens recognized by polyclonal or monoclonal antibodies. This unit provides protocols for all steps, starting with solubilization of the protein samples, usually by means of SDS and reducing agents. Following solubilization, the material is separated by SDS-PAGE and the antigens are electrophoretically transferred to a membrane, a process that can be monitored by reversible staining with Ponceau S. The transferred proteins are bound to the surface of the membrane, providing access to immunodetection reagents. After nonspecific binding sites are blocked, the membrane is probed with the primary antibody and washed. The antibody-antigen complexes are tagged with fluorophores, horseradish peroxidase, or alkaline phosphatase coupled to a secondary anti-IgG antibody, and detected using appropriate fluorescent imaging technologies or with chromogenic or luminescent substrates. Finally, membranes may be stripped and reprobed.

Analysis of protein stability and ligand interactions by thermal shift assay

Purification of recombinant proteins for biochemical assays and structural studies is time-consuming and presents inherent difficulties that depend on the optimization of protein stability. The use of dyes to monitor thermal denaturation of proteins with sensitive fluorescence detection enables rapid and inexpensive determination of protein stability using real-time PCR instruments. By screening a wide range of solution conditions and additives in a 96-well format, the thermal shift assay easily identifies conditions that significantly enhance the stability of recombinant proteins. The same approach can be used as an initial low-cost screen to discover new protein-ligand interactions by capitalizing on increases in protein stability that typically occur upon ligand binding. This unit presents a methodological workflow for small-scale, high-throughput thermal denaturation of recombinant proteins in the presence of SYPRO Orange dye.

Immunoblotting and immunodetection

Immunoblotting (western blotting) is used to identify specific antigens recognized by polyclonal or monoclonal antibodies. This unit provides protocols for all steps, starting with solubilization of the protein samples, usually by means of SDS and reducing agents. Following solubilization, the material is separated by SDS-PAGE and the antigens are electrophoretically transferred to a membrane, a process that can be monitored by reversible staining with Ponceau S. The transferred proteins are bound to the surface of the membrane, providing access to immunodetection reagents. After nonspecific binding sites are blocked, the membrane is probed with the primary antibody and washed. The antibody-antigen complexes are tagged with horseradish peroxidase or alkaline phosphatase coupled to a secondary anti-IgG antibody, and detected using appropriate chromogenic or luminescent substrates. Finally, membranes may be stripped and reprobed.