Consider a protein composed of six subunits, three identical high-molecular weight subunits and three identical low molecular weight subunits. A researcher runs a purified sample of this protein on a typical SDS-polyacrylamide gel with the positive pole on the bottom and the negative pole at the top and the protein in the gel is then stained. The researcher would most likely observe bands; the band closest to the bottom of the gel would represent the molecular weight subunit.