ligations

Ligation is the act of binding or tying one structure to another. In science and medicine, ligation refers to the joining of two molecules, strands, or structures, typically by forming chemical bonds or by securing tissues with a ligature. The term derives from Latin ligare, meaning to bind.

In molecular biology, DNA ligation is the enzymatic joining of DNA strands by ligase enzymes. It is a core step in cloning, genetic engineering, and DNA assembly, enabling insertion of fragments into vectors. Ligation is influenced by end compatibility (sticky versus blunt ends), DNA concentration, temperature, and the presence of cofactors. After digestion with restriction enzymes, compatible ends are joined to create a continuous DNA molecule.

In chemistry and chemical biology, ligation denotes non-enzymatic joining of molecules or macromolecules. Native chemical ligation, a widely used method, connects two unprotected peptide segments via a C-terminal thioester and an N-terminal cysteine to form a native peptide bond, enabling protein semisynthesis. Other ligation strategies employ click chemistry, oxime ligation, or hydrazone formation to link functional modules in polymers and biomaterials.

In medicine, ligation commonly means tying off vessels, ducts, or tissues to stop bleeding or permanently occlude a lumen. Surgical ligation may involve sutures, clips, or staples. Tubal ligation is a well-known sterilization procedure in which the fallopian tubes are tied or blocked. Ligation techniques carry risks such as infection or unintended tissue damage and are chosen based on indication and anatomy.