Which technique separates proteins based on their size?

The technique that separates proteins based on their size is polyacrylamide gel electrophoresis, commonly referred to as SDS-PAGE. This method utilizes a polyacrylamide gel matrix through which proteins migrate when an electric current is applied. The size of the proteins determines their rate of movement through the gel—larger proteins travel more slowly, while smaller proteins move more quickly. This size-based separation is primarily due to the denaturing nature of SDS (sodium dodecyl sulfate), which coats the proteins with a uniform negative charge and eliminates the effects of secondary and tertiary structures. As a result, SDS-PAGE allows for effective size discrimination of the proteins in a sample.

Other techniques listed have different principles of separation or measurement. Western blotting is used for detecting specific proteins after separation but does not inherently separate proteins by size on its own, as it relies on prior electrophoretic separation. Column chromatography separates molecules based on various attributes like size or affinity but is not exclusively size-based and involves a different setup and methodology. Enzyme-linked immunosorbent assay (ELISA) is primarily a quantitative technique aimed at measuring specific proteins or antigens using enzyme-linked antibodies, which does not involve physical separation based on size. Thus