Bands Appear Higher Than Expected Molecular Weight (Western Blot (Bands at Wrong MW))

Question

Accepted Answer

All protein bands or the target band remain near the top of the membrane, migrating less than expected based on the predicted molecular weight. Coomassie blue staining confirms abnormally high band positions before immunostaining. Common causes: 1) Gel electrophoresis run time insufficient for proteins to migrate adequate distance through gel matrix 2) Excessive acrylamide percentage in the gel for the target protein molecular weight, creating excessive matrix resistance 3) Voltage too low (<100V) during electrophoresis, slowing protein migration below optimal separation conditions 4) High molecular weight proteins (>100 kDa) run in gel formulation designed for smaller proteins Solutions: 1) Extend gel running time according to manufacturer recommendations, monitoring ladder marker separation until target protein range is adequately resolved 2) Use lower acrylamide percentage gels (6-10%) for higher molecular weight proteins (>100 kDa) 3) Run gel at appropriate voltage (100-150V) for 1-2 hours to achieve proper protein separation 4) Verify Coomassie blue staining of transferred membrane before proceeding with blocking to assess if additional run time is needed