42.
The use of insulin hormone to purify its receptor is an example of

• (A) Ion exchange chromatography
• (B) Affinity chromatography
• (C) Gel filtration chromatography
• (D) Ligand mediated chromatography

  Answer: (B) Affinity chromatography

  Using insulin hormone to purify its receptor exemplifies affinity chromatography, which relies on the specific, high-affinity binding between a ligand (insulin) and its target receptor.

  Option Analysis

  (A) Ion Exchange Chromatography

  This technique separates proteins based on net surface charge using charged resins, with elution via salt gradients or pH changes.[ from previous]
  It lacks the specific ligand-receptor interaction needed for insulin receptor purification.

  (B) Affinity Chromatography

  Affinity chromatography immobilizes a specific ligand like insulin on a matrix (e.g., agarose beads), capturing only the insulin receptor through reversible, biospecific binding.
  The receptor is then eluted with competitive agents, buffers, or denaturants, achieving high purity (up to 250,000-fold).

  (C) Gel Filtration Chromatography

  Known as size-exclusion, it separates proteins by hydrodynamic size as they pass through porous beads, with larger molecules eluting first.[ from previous]
  No ligand specificity; unsuitable for receptor purification based on insulin binding.

  (D) Ligand Mediated Chromatography

  This is not a standard classification but overlaps with affinity chromatography, where ligands mediate binding—however, affinity is the precise, recognized term in biochemistry for this application.​

  Affinity chromatography using insulin hormone to purify its receptor is a classic example in biochemistry, highlighting ligand-specific binding for high-purity isolation. This method is crucial for GATE Life Sciences aspirants studying protein purification techniques.

  Mechanism of Insulin Receptor Purification

  Insulin is covalently linked to a solid matrix like agarose, creating an affinity column that selectively binds the insulin receptor from cell extracts (e.g., liver membranes).
  The receptor-ligand complex forms due to high-affinity interactions (Kd in nM range), followed by elution with urea buffers or pH shifts for 50-80% recovery.
  This achieves near-theoretical purity, far superior to non-specific methods.​

  Protein Purification Techniques Comparison

  Technique	Basis of Separation	Insulin Receptor Suitability
  Ion Exchange Chromatography	Net charge ​	Low; non-specific
  Affinity Chromatography	Ligand-receptor binding	Ideal; high specificity
  Gel Filtration Chromatography	Size ​	None; size-based only
  Ligand Mediated (Affinity variant)	Ligand interaction ​	Valid but not standard term

  This comparison clarifies why affinity chromatography is the correct choice for insulin-based receptor purification in competitive exams.​

  GATE Exam Applications

  Essential for questions on receptor isolation in endocrinology and molecular biology; often paired with prior charge-based methods like ion exchange.​
  Mastering this boosts scores in biochemistry sections.