Which method is primarily used to separate proteins based on their size?

Gel filtration chromatography is primarily used to separate proteins based on their size. This technique, also known as size-exclusion chromatography, utilizes a column filled with porous beads. As a protein solution is passed through this column, smaller proteins can enter the pores of the beads, which delays their elution compared to larger proteins that cannot enter the pores and thus travel more quickly through the column.

This method effectively separates proteins based on their molecular weight, allowing researchers to isolate specific proteins from a mixture based on their size. It is commonly used in various applications, including protein purification processes, where removing smaller peptides or contaminants is essential to obtain a protein of interest in its purest form.

Other methods, such as affinity chromatography, are more dependent on the specific interactions between proteins and ligands, while western blotting is employed to detect specific proteins after they have already been separated, and mass spectrometry is used for determining the mass and structure of molecules rather than directly for size separation.