Organic Chemistry MCAT Practice Exam

What is the main purpose of affinity chromatography?

1. To separate compounds based on boiling point.

2. To elute proteins by changing the pH.

3. To separate proteins using antibody-binding interactions.

4. To retain molecules with high volatility.

The correct answer is: To separate proteins using antibody-binding interactions.

Affinity chromatography is a powerful technique used primarily for the purification of proteins and other biomolecules based on their specific interactions with a ligand that is immobilized on a chromatography matrix. The main purpose of this technique is to exploit the high specificity of biological interactions. In this method, a target protein is first introduced into a column that contains a stationary phase with a ligand that specifically binds to that protein. Because of this selective binding, the target proteins are retained, while other components of the mixture can be washed away. Afterward, the target proteins can be eluted from the column by changing conditions (like utilizing a solution that competes for binding, altering pH, or changing ionic strength). This method stands out from other techniques such as size-exclusion chromatography or ion-exchange chromatography, which do not specifically target unique molecular interactions. The use of antibody-binding interactions in affinity chromatography enables the effective isolation of a protein of interest within a complex mixture, making it a widely used tool in biochemistry and molecular biology.