Peptide Bond
Definition
A peptide bond is the covalent chemical bond formed between the carboxyl group (-COOH) of one amino acid and the amino group (-NH₂) of another through a condensation reaction that releases water. It is the fundamental linkage that joins amino acids into peptide chains and proteins.
Chemistry and Properties
The peptide bond has partial double-bond character due to resonance between the C=O and C-N bonds, which constrains rotation and forces the bond into a planar configuration. This planarity is critical for protein secondary structure — it defines the geometry of alpha helices and beta sheets.
Key properties include:
- Planarity — The six atoms of the peptide unit (Cα, C, O, N, H, Cα) lie in a plane
- Trans configuration — Most peptide bonds adopt the trans conformation (except before proline, where cis is more common)
- Stability — Peptide bonds are kinetically stable under physiological conditions but susceptible to enzymatic hydrolysis by proteases
- Directionality — Peptide chains have an N-terminus (free amino group) and C-terminus (free carboxyl group)
Relevance to Peptide Research
Understanding peptide bonds is fundamental to peptide science. Proteases cleave peptide bonds at specific sequences, determining a peptide’s half-life in biological systems. Researchers modify peptide bonds to improve stability — strategies include N-methylation, incorporation of D-amino acids, use of peptidomimetic bonds (e.g., reduced amide bonds, thioamides), and cyclisation. These modifications are central to designing research peptides with improved pharmacokinetic profiles.
Related Peptides
Peptide profiles that reference “Peptide Bond” in their research content.