What type of proteins will bind in cation-exchange chromatography?

• A. Negatively charged proteins
• B. Positively charged proteins
• C. Neutral proteins
• D. Large proteins

Answer: (B)

In cation-exchange chromatography, the technique relies on the principles of ionic interactions between charged proteins and the stationary phase of the chromatography column. The stationary phase is composed of negatively charged groups that attract and bind positively charged proteins, which are cations.

When a sample containing proteins is introduced into the column, the positively charged proteins will interact with the negatively charged resin, allowing for separation based on their charge. Negatively charged proteins would not bind to the negatively charged matrix and would flow through the column, while neutral proteins would also not have a strong interaction with the charged resin and would not be retained effectively. The size of the proteins is relevant in some contexts but does not determine their binding in this specific type of chromatography.

Thus, the proteins that effectively bind in cation-exchange chromatography are the positively charged ones, as they are attracted to the negatively charged stationary phase.