Inchemistry andbiochemistry, anoligomer (/əˈlɪɡəmər/ ⓘ) is amolecule that consists of a fewrepeating units which could be derived, actually or conceptually, from smaller molecules,monomers.[1][2][3] The name is composed ofGreek elementsoligo-, "a few" and-mer, "parts". Anadjective form isoligomeric.[3]
The oligomer concept is contrasted to that of apolymer, which is usually understood to have a large number of units, possibly thousands or millions. However, there is no sharp distinction between these two concepts. One proposed criterion is whether the molecule's properties vary significantly with the removal of one or a few of the units.[3]
An oligomer with a specific number of units is referred to by the Greek prefix denoting that number, with the ending-mer: thusdimer,trimer,tetramer,pentamer, andhexamer refer to molecules with two, three, four, five, and six units, respectively. The units of an oligomer may be arranged in a linear chain (as inmelam, a dimer ofmelamine); a closed ring (as in1,3,5-trioxane, acyclic trimer offormaldehyde); or a more complex structure (as intellurium tetrabromide, a tetramer ofTeBr4 with acube-like core). If the units are identical, one has ahomo-oligomer; otherwise one may usehetero-oligomer. An example of a homo-oligomeric protein iscollagen, which is composed of three identical protein chains.
Some biologically important oligomers are macromolecules likeproteins ornucleic acids; for instance,hemoglobin is a protein tetramer. An oligomer ofamino acids is called an oligopeptide or just apeptide. Anoligosaccharide is an oligomer ofmonosaccharides (simple sugars). Anoligonucleotide is a short single-stranded fragment ofnucleic acid such asDNA orRNA, or similar fragments of analogs of nucleic acids such aspeptide nucleic acid orMorpholinos.
The units of an oligomer may be connected bycovalent bonds, which may result from bond rearrangement orcondensation reactions, or by weaker forces such ashydrogen bonds.The termmultimer (/ˈmʌltɪmər/) is used in biochemistry for oligomers of proteins that are not covalently bound. Themajor capsid protein VP1 that comprises the shell ofpolyomaviruses is a self-assembling multimer of 72 pentamers held together by local electric charges.
Manyoils are oligomeric, such asliquid paraffin.Plasticizers are oligomericesters widely used to softenthermoplastics such asPVC. They may be made from monomers by linking them together, or by separation from the higher fractions ofcrude oil.Polybutene is an oligomeric oil used to makeputty.
Oligomerization is a chemical process that converts monomers to macromolecular complexes through a finitedegree of polymerization.[3]Telomerization is an oligomerization carried out under conditions that result inchain transfer, limiting the size of the oligomers.[4][3] (This concept is not to be confused with the formation of atelomere, a region of highly repetitive DNA at the end of achromosome.)
In the oil and gas industry, green oil refers to oligomers formed in all C2, C3, and C4 hydrogenation reactors of ethylene plants and other petrochemical production facilities; it is a mixture of C4 to C20 unsaturated and reactive components with about 90%aliphaticdienes and 10% ofalkanes plusalkenes.[5] Different heterogeneous and homogeneous catalysts are operative in producing green oils via the oligomerization of alkenes.[6]
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