Final answer:
Increased ionic strength in ion exchange chromatography leads to the elution of proteins by adding small ions that compete for binding sites on the resin, thus displacing the protein molecules. This is referred to as the 'salting-out' effect.The correct answer is option C.
Step-by-step explanation:
In ion exchange chromatography, increased ionic strength elutes proteins from an ion exchange column by adding small ions that compete with the charged groups of the macromolecules for sites on the resin. The correct answer to the question is option C) It adds small ions to compete with the charged groups of the macromolecules for sites on the resin. When salts like KCl are added to the column, the K+ and Cl- ions surround the protein molecules with a layer of water molecules, resulting in a reduced interaction between the protein and the ion exchange resin, allowing the protein to be eluted.
Ion exchange chromatography exploits the charge properties of proteins. Proteins are bound to the column based on their charge at a given pH. When the ionic strength of the buffer is increased, there are more ions available to bind to the resin, which then displaces the protein molecules due to competitive binding. This process, known as salting-out, is influenced by the nature of the protein's interactions with the surrounding ions and water molecules.