Electrophoretic mobility shift assays (EMSAs) are among the most frequently used and straightforward experiments for studying protein-nucleic acid interactions. EMSAs rely on the principle that protein-nucleic acid complexes have reduced electrophoretic mobility in a native gel matrix compared to free nucleic acid due to their larger size and reduced negative charge. Therefore, bands for the protein-nucleic acid complexes are shifted in a gel and can be distinguished from free nucleic acids. EMSAs remain a popular technique since they do not require specialist equipment and the complexes formed are easily visualized. Furthermore, the technique can be adapted to enable various aspects of protein-nucleic acid interactions to be investigated, including sequence specificity, estimated binding affinity, and binding stoichiometry.
Keywords: Affinity measurement; Band shift assay; EMSA; Electrophoretic mobility shift assay; Protein–DNA interactions; Protein–RNA interactions.