Which chromatography technique is used to separate proteins based on size differences?

• A. Ion exchange chromatography
• B. Gel filtration chromatography
• C. Affinity chromatography
• D. High-performance liquid chromatography

Answer: (B)

Gel filtration chromatography is specifically designed to separate proteins based on their size. This technique operates on the principle of size exclusion, where a porous gel matrix allows smaller molecules to enter the pores while larger molecules are excluded from entering. As a result, larger proteins elute first because they pass through the column more quickly, while smaller proteins take longer to elute as they navigate through the pores of the gel.

The effectiveness of gel filtration chromatography for protein separation lies in its ability to differentiate molecules based solely on their physical size, which is crucial for applications where precise separation of protein oligomers or multimers is needed. This method can be used to resolve a range of proteins effectively, making it a valuable tool in protein purification processes.

Other techniques like ion exchange chromatography focus on the charge of proteins, affinity chromatography exploits specific binding interactions, and high-performance liquid chromatography can be used for a variety of separation methods but does not specialize solely in size-based separation. Thus, gel filtration stands out in its application for the separation of proteins by size.