Practice question

Electrophoretic Mobility Shift Assay is a classic in vitro technique for studying nucleic acid-protein interactions. A radiolabeled or fluorescent double-stranded DNA fragment containing putative protein binding motif is incubated with nuclear extract or purified protein. If specific binding protein recognizes sequence, formation of protein-DNA complex increases molecular mass and reduces net negative charge, causing retardation during non-denaturing polyacrylamide gel electrophoresis compared to free probe. The assay can also detect protein-protein interactions via supershift when additional partner increases complex size. It does not measure protein degradation or folding status directly.