nounIntermediate
Definition
Bond-forming reaction that releases a water molecule; the fundamental mechanism by which peptide bonds are created during translation and in laboratory synthesis.

Detailed Explanation

In a condensation reaction, the carboxyl group (–COOH) of one amino acid reacts with the amino group (–NH₂) of another, releasing one molecule of water (H₂O) and forming a covalent peptide bond (–CO–NH–). This reaction is thermodynamically unfavorable under standard conditions (ΔG ≈ +2–4 kcal/mol), which is why biological systems require the energy input of ATP and the catalytic machinery of the ribosome to drive it forward. In laboratory SPPS, coupling reagents (HATU, HBTU, DIC) activate the carboxyl group to make the reaction favorable. The reverse of condensation is hydrolysis — breaking a peptide bond by adding water.

Key Facts

  • In a condensation reaction, the carboxyl group (–COOH) of one amino acid reacts with the amino group (–NH₂) of another, releasing one molecule of water (H₂O) and forming a covalent peptide bond (–CO–NH–)
  • This reaction is thermodynamically unfavorable under standard conditions (ΔG ≈ +2–4 kcal/mol), which is why biological systems require the energy input of ATP and the catalytic machinery of the ribosome to drive it forward
  • In laboratory SPPS, coupling reagents (HATU, HBTU, DIC) activate the carboxyl group to make the reaction favorable
  • The reverse of condensation is hydrolysis — breaking a peptide bond by adding water
Related Terms Peptide Bond Hydrolysis SPPS Coupling Reagent Amino Acid

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