Super-shift EMSA Service
Antibody-Based Confirmation of EMSA Complexes
CD BioSciences provides Super-shift EMSA services to help evaluate whether an observed shifted EMSA complex contains a target protein. The assay uses a target-specific antibody in the binding reaction and is commonly applied as a follow-up to protein-DNA or protein-RNA EMSA experiments.
Super-shift EMSA can provide useful protein identity evidence, but the result depends on antibody quality, epitope accessibility, and the stability of the protein-probe complex. Therefore, project design should include appropriate controls and realistic interpretation criteria.
Principle of Super-shift EMSA
In a super-shift assay, a target-specific antibody is added to the EMSA binding reaction. If the antibody binds to the protein within the protein-probe complex, the larger antibody-protein-probe complex may migrate more slowly than the original shifted complex, producing a super-shifted band. In some cases, antibody binding may reduce or disrupt the original shifted band instead of forming a clear slower band.
Figure 1. Principle of antibody-based super-shift EMSA.
When Super-shift EMSA Is Recommended
When a shifted band has been observed and additional evidence is needed to support the involvement of a specific protein.
When multiple DNA- or RNA-binding proteins may be present in the sample and target protein identity requires further assessment.
When EMSA is used to support transcriptional regulation or RNA-protein interaction models.
When sequence specificity has been assessed and protein identity confirmation is the next experimental question.
Antibody and Control Requirements
The success of super-shift EMSA is strongly influenced by antibody compatibility. An antibody that works in Western blot may not always work in EMSA because the relevant epitope may be masked in the native protein-probe complex.
Figure 2. Representative super-shift EMSA control layout.
- Free probe control
- Protein sample with labeled probe
- Target-specific antibody treatment
- Control antibody treatment, if available
- Antibody-only control
- Competitor probe control, when specificity assessment is required
Important Notes
Super-shift EMSA should not be described as guaranteed target confirmation. A negative or unclear super-shift may result from poor antibody compatibility, inaccessible epitopes, weak binding, unstable complexes, or assay condition changes caused by antibody addition.
| Observation | Possible Interpretation |
|---|---|
| Slower super-shifted band | The antibody may bind to the protein-probe complex, supporting target protein involvement. |
| Reduced original shifted band | The antibody may interfere with complex formation or alter complex mobility. |
| No visible change | The antibody may be incompatible with native EMSA conditions or the target protein may not be part of the complex. |
Information Required
- Existing EMSA result or planned validation design
- Target protein name and species
- Probe sequence and protein sample source
- Target-specific antibody information
- Control antibody availability, if any
- Number of groups and expected comparison design
Deliverables
- Super-shift EMSA lane design
- Antibody and control setup record
- Original gel images
- Result interpretation with limitations noted
- Standard experimental report
Related Services
Please contact us with your EMSA result, target protein information, probe sequence, and antibody information for super-shift EMSA feasibility evaluation.
For research use only, not for clinical use.