Peptidbinding

Peptidbinding is the covalent amide bond that links amino acids in peptides and proteins. It forms between the carboxyl group of one amino acid and the amino group of the next, releasing a molecule of water in a condensation reaction. In cells, peptide bonds are created during protein synthesis on the ribosome, where the peptidyl transferase activity catalyzes bond formation using energy from charged tRNAs. In laboratory chemistry, peptide bonds can be formed by various coupling methods.

Chemically, the peptide bond exhibits partial double-bond character due to resonance between the carbonyl group and the amide nitrogen. This resonance restricts rotation around the C–N bond and makes the peptide backbone effectively planar. The bond length is shorter than a typical C–N single bond, and the geometry around the bond is fixed, influencing the overall conformation of the polypeptide. The backbone dihedral angles, phi and psi, describe possible conformations. Most peptide bonds are in the trans configuration, which minimizes steric clashes; cis configurations are rare, though bonds involving proline show a higher tendency to adopt cis geometry.

Biologically, the peptide bond is essential for the construction of proteins and determines much of their structure and function. The stability of the bond under physiological conditions supports the formation of secondary structures such as alpha helices and beta sheets. Hydrolysis of the peptide bond breaks the linkage, yielding amino acids; this reaction is catalyzed by proteases in living organisms and by acid, base, or specific enzymes in chemical or enzymatic processes.