How Do I Determine the Apparent Molecular Weight of a Protein?

Some proteins migrate anomalously on SDS gels; therefore the molecular weight estimate obtained is referred to as the apparent molecular weight. When determining the apparent molecular weight of a protein, do not compare your protein of interest to prestained protein molecular weight markers. Prestained molecular weight markers will run differently than unstained proteins; use unstained protein molecular weight markers and stain the gel after electrophoresis.