Why Do Closely Sized Proteins Behave Differently During SDS PAGE Electrophoresis?
When you analyze proteins with nearly identical molecular weights, you may expect them to migrate similarly during gel electrophoresis. However, your experimental results can reveal unexpected differences in band position, intensity, or separation patterns. Two proteins with closely related molecular sizes may behave differently because their structural characteristics, amino acid composition, post-translational modifications, and sample conditions influence their migration. Understanding these variations helps you interpret electrophoretic results more accurately and avoid overlooking important protein differences. 1. Molecular Weight Is Not the Only Factor Affecting Protein Migration SDS-PAGE separates proteins primarily according to their apparent molecular weight. Sodium dodecyl sulfate (SDS) denatures most proteins and gives them a relatively uniform negative charge-to-mass ratio. This allows proteins to move through a polyacrylamide gel according to their size. However, thi...