In ion exchange chromatography, how can proteins be eluted from cation exchange resins?

In ion exchange chromatography, proteins bound to cation exchange resins can be eluted by increasing the salt concentration in the mobile phase. Cation exchange resins have negatively charged groups that attract and bind positively charged proteins. When the salt concentration is increased, the ions from the salt compete with the positively charged proteins for binding sites on the resin. As a result, the increased concentration of competing cations disrupts the interaction between the proteins and the resin, allowing the bound proteins to be eluted from the column.

The process is based on the principle that higher concentrations of ions in the solution can effectively displace the bound proteins, facilitating their release from the cation exchange resin. This method is commonly used because it provides a controlled way to elute proteins while maintaining their functional integrity, compared to other methods that might denature proteins or alter their structure.