dimeri

Dimeri, or dimers in English, are molecular complexes formed by two monomer units. In chemistry and biochemistry, a dimer can arise from covalent linking or from noncovalent interactions, and it may be either a homodimer (two identical subunits) or a heterodimer (two different subunits). Dimers can be stable species or transient intermediates depending on conditions such as concentration, pH, and redox state.

In proteins, dimers are common functional units. Noncovalent dimers form through hydrophobic, electrostatic, and hydrogen-bonding interactions, while covalent dimers are held together by disulfide bonds. Dimerization is key to the activity of many receptors, including receptor tyrosine kinases, which often require dimer formation to initiate signaling. Transcription factors may function as dimers (for example, basic leucine zipper proteins) to recognize DNA. Dimers also occur in enzymes, where two subunits cooperate in catalysis.

Dimers form through association reactions M + M ⇌ D, with an equilibrium constant K = [D]/[M]^2. The extent of dimerization depends on concentration, temperature, solvent, and redox conditions. Analytical methods used to study dimers include size-exclusion chromatography, analytical ultracentrifugation, native electrophoresis, mass spectrometry, and structural techniques like X-ray crystallography and SAXS.

Biological and technological relevance: dimerization can regulate activity, stability, and specificity. Aberrant dimerization is linked to diseases and dysregulated signaling, and controlled dimer formation is exploited in protein engineering and material science.