Dimerisation

Dimerisation is the process by which two molecular units, or monomers, join to form a dimer, a species composed of two units. Dimers can be held together by covalent bonds or by non-covalent interactions and may be reversible or irreversible depending on the bonding type and conditions. Dimerisation is observed across chemistry, biochemistry, and materials science and can affect reactivity, stability, and function.

There are several modes of dimerisation. Covalent dimerisation involves actual chemical bonds, such as disulfide linkages between cysteine residues in proteins or carbon–carbon bonds formed in synthetic reactions. Non-covalent dimerisation relies on hydrogen bonding, ionic interactions, π–π stacking, and van der Waals forces. A distinct category is photodimerisation, where light exposure induces dimer formation, as in certain alkenes forming cyclobutane dimers; photodimers can be reversible under certain conditions.

In biology, dimerisation is a common mechanism for regulating activity. Many transcription factors and cell-surface receptors function as dimers, with dimer formation influencing DNA binding, signaling, and allosteric control. Dimers can be homo-dimers (two identical units) or hetero-dimers (two different units). In materials and polymer science, dimerisation can serve as an initial step toward higher-order assemblies and can affect properties such as strength, electronic behavior, and optical characteristics.

Factors that influence dimerisation include concentration, temperature, solvent and pH, and the presence of catalysts or mutations. The process can be cooperative and reversible, enabling dynamic control of function in biological systems or tunable properties in materials. Detection and characterization commonly employ spectroscopy, mass spectrometry, analytical ultracentrifugation, and crystallography.