An oligomer (from ancient Greek ὀλίγοι oligoi 'few' and μέρος méros 'part') is a molecule that is made up of several structurally identical or similar units. If there is a larger number of units, one speaks of a polymer . The distinguishing criterion according to IUPAC is whether a small change in the number of units causes a significant change in properties. The process of forming oligomers is known as oligomerization .
A single unit is called a monomer . According to the number of units, oligomers are usually named based on ancient Greek numerals : if they consist of two, three, four, five, six, seven, eight ... units they are called dimer , trimer , tetramer , pentamer, hexamer, heptamer, octamer.
If all subunits are identical to one another, one speaks of a homomeric oligomer or homomer , in the case of different subunits of a heteromer .
Use of language in biochemistry
The units of an oligomer are linked to one another. In the case of an oligopeptide, for example, this is a covalent bond, the peptide bond . However, amino acid chains of an oligopeptide or polypeptide formed in this way can fold into a protein and, in turn, assemble with other proteins to form a larger complex, to associate to form a protein complex . However, its subunits are usually not covalently linked to one another.
In biochemistry, an “oligomeric protein ” is not understood to be a protein made up of just a few amino acid units, that would be an oligopeptide, but a protein complex made up of several - equal or unequal - subunits. For example, a collagen fiber is a homomeric trimer , whereas hemoglobin is a heteromeric tetramer or heterotetramer .
- -mer : Notes on the -mer suffix