Peptide Bond

A peptide bond is a covalent amide linkage formed between the alpha-carboxyl group of one amino acid and the alpha-amino group of another, with the release of a water molecule (condensation reaction). This bond is the fundamental chemical connection that links amino acids together to form peptides and proteins. The peptide bond exhibits partial double-bond character due to resonance between the carbonyl oxygen and the amide nitrogen, which restricts rotation around the C-N axis and forces the bond into a planar configuration. This planarity is critical for the higher-order folding patterns (alpha helices, beta sheets) that determine a peptide's three-dimensional structure and biological activity. Peptide bonds are thermodynamically stable but kinetically labile, meaning they can be cleaved by specific proteolytic enzymes (proteases), which is why many therapeutic peptides require modifications or specialised delivery systems to resist enzymatic degradation in vivo.