In affinity chromatography, provide a typical ligand-target pair used in practice.

In affinity chromatography, provide a typical ligand-target pair used in practice.

• A. His-tagged proteins binding to Ni2+-NTA resin.
• B. Proteins binding to silica via hydrophobic interactions.
• C. Small molecules binding to non-specific resin.
• D. DNA fragments binding to polymer beads.

Answer: (C)

Affinity chromatography relies on a highly specific interaction between a ligand fixed on the resin and a particular target in the sample. A typical and widely used pairing is a His-tagged protein binding to a Ni2+-NTA resin. The histidine residues in the tag coordinate with the nickel ions chelated by the NTA groups on the resin, creating a strong, selective affinity that retains the tagged protein while most other proteins flow through. Elution is usually achieved by introducing imidazole (which competes with histidine for nickel) or by lowering the pH, releasing the protein under mild conditions that help preserve activity. This approach is popular because it’s straightforward, fast, and compatible with many buffers and workflows. Other scenarios described—proteins binding to silica by hydrophobic interactions, small molecules binding to non-specific resin, or DNA fragments binding to generic beads—lack the defined ligand-target specificity that characterizes affinity chromatography, so they aren’t typical examples of this technique.

Affinity chromatography relies on a highly specific interaction between a ligand fixed on the resin and a particular target in the sample. A typical and widely used pairing is a His-tagged protein binding to a Ni2+-NTA resin. The histidine residues in the tag coordinate with the nickel ions chelated by the NTA groups on the resin, creating a strong, selective affinity that retains the tagged protein while most other proteins flow through. Elution is usually achieved by introducing imidazole (which competes with histidine for nickel) or by lowering the pH, releasing the protein under mild conditions that help preserve activity. This approach is popular because it’s straightforward, fast, and compatible with many buffers and workflows. Other scenarios described—proteins binding to silica by hydrophobic interactions, small molecules binding to non-specific resin, or DNA fragments binding to generic beads—lack the defined ligand-target specificity that characterizes affinity chromatography, so they aren’t typical examples of this technique.