Oligomer

In <a href="/facts/Chemistry/SrNqkGVm">chemistry</a> and <a href="/facts/Biochemistry/fa2pWEBp">biochemistry</a>, an oligomer is a <a href="/facts/Molecule/N9ljSfFq">molecule</a> that consists of a few <a href="/facts/Repeating_unit/WIxA68X4">repeating units</a> which could be derived, actually or conceptually, from smaller molecules, <a href="/facts/Monomer/Gw3CltMb">monomers</a>. The name is composed of <a href="/facts/Greek_language/pzDd6eIz">Greek</a> elements oligo-, "a few" and -mer, "parts". An <a href="/facts/Adjective/0ohBjtmT">adjective</a> form is oligomeric. 
The oligomer concept is contrasted to that of a <a href="/facts/Polymer/eF32E50K">polymer</a>, 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. 
An oligomer with a specific number of units is referred to by the Greek prefix denoting that number, with the ending -mer: thus <a href="/facts/Dimer_(chemistry)/mU64PnEq">dimer</a>, <a href="/facts/Trimer_(chemistry)/ws3JkjuQ">trimer</a>, <a href="/facts/Tetramer/qeUFnwC4">tetramer</a>, <a href="/facts/Pentamer/JUdMmxlg">pentamer</a>, and <a href="/facts/Hexamer/v7oDY8zu">hexamer</a> 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 in <a href="/facts/Melam_(chemistry)/yYc0nfyu">melam</a>, a dimer of <a href="/facts/Melamine/wvvc4rrz">melamine</a>); a closed ring (as in <a href="/facts/1%2c3%2c5-trioxane/I7WIEnBd">1,3,5-trioxane</a>, a <a href="/facts/Cyclic_compound/TH2ReKIQ">cyclic</a> trimer of <a href="/facts/Formaldehyde/Ck8RLfqk">formaldehyde</a>); or a more complex structure (as in <a href="/facts/Tellurium_tetrabromide/w6XsXj42">tellurium tetrabromide</a>, a tetramer of TeBr4 with a <a href="/facts/Cube/65lUaAqN">cube</a>-like core). If the units are identical, one has a homo-oligomer; otherwise one may use hetero-oligomer. An example of a homo-oligomeric protein is <a href="/facts/Collagen/KsyAb72K">collagen</a>, which is composed of three identical protein chains.

Some biologically important oligomers are macromolecules like <a href="/facts/Protein/Jxmagu3E">proteins</a> or <a href="/facts/Nucleic_acids/2tTgcI0v">nucleic acids</a>; for instance, <a href="/facts/Hemoglobin/RsD1MzYA">hemoglobin</a> is a protein tetramer. An oligomer of <a href="/facts/Amino_acid/WDxYwBny">amino acids</a> is called an oligopeptide or just a <a href="/facts/Peptide/C4ltc7UG">peptide</a>. An <a href="/facts/Oligosaccharide/5to180o3">oligosaccharide</a> is an oligomer of <a href="/facts/Monosaccharide/yzs2d6Eq">monosaccharides</a> (simple sugars). An <a href="/facts/Oligonucleotide/Gc99fPnC">oligonucleotide</a> is a short single-stranded fragment of <a href="/facts/Nucleic_acid/2tTgcI0v">nucleic acid</a> such as <a href="/facts/Deoxyribonucleic_acid/nB89Iauz">DNA</a> or <a href="/facts/Ribonucleic_acid/HxPeNfNj">RNA</a>, or similar fragments of analogs of nucleic acids such as <a href="/facts/Peptide_nucleic_acid/9MkVaqXK">peptide nucleic acid</a> or <a href="/facts/Morpholino/EsU9Heor">Morpholinos</a>.

The units of an oligomer may be connected by <a href="/facts/Covalent_bond/EzMLf3Pz">covalent bonds</a>, which may result from bond rearrangement or <a href="/facts/Condensation_reaction/wMG0F6La">condensation reactions</a>, or by weaker forces such as <a href="/facts/Hydrogen_bond/85V86IIg">hydrogen bonds</a>.

The term multimer (/ˈmʌltɪmər/) is used in biochemistry for oligomers of proteins that are not covalently bound. The <a href="/facts/Major_capsid_protein_VP1/zhMgV2V1">major capsid protein VP1</a> that comprises the shell of <a href="/facts/Polyomavirus/2PSmXlGm">polyomaviruses</a> is a self-assembling multimer of 72 pentamers held together by local electric charges.
Many <a href="/facts/Oil/fsgX2IRM">oils</a> are oligomeric, such as <a href="/facts/Liquid_paraffin_(medicinal)/FgSPj6ro">liquid paraffin</a>. <a href="/facts/Plasticizers/RjzuplRY">Plasticizers</a> are oligomeric <a href="/facts/Ester/FoUAIIw4">esters</a> widely used to soften <a href="/facts/Thermoplastics/5KJB8dwN">thermoplastics</a> such as <a href="/facts/Polyvinyl_chloride/9VkegJvr">PVC</a>. They may be made from monomers by linking them together, or by separation from the higher fractions of <a href="/facts/Crude_oil/IQV0bHVd">crude oil</a>. <a href="/facts/Polybutene/17kweInR">Polybutene</a> is an oligomeric oil used to make <a href="/facts/Putty/eNhqRU2v">putty</a>. 
Oligomerization is a chemical process that converts monomers to macromolecular complexes through a finite <a href="/facts/Degree_of_polymerization/1WYmrcNk">degree of polymerization</a>. <a href="/facts/Telomerization/dBujThPG">Telomerization</a> is an oligomerization carried out under conditions that result in <a href="/facts/Chain_transfer/G2uQ7Qay">chain transfer</a>, limiting the size of the oligomers. (This concept is not to be confused with the formation of a <a href="/facts/Telomere/RQ4Gp9LT">telomere</a>, a region of highly repetitive DNA at the end of a <a href="/facts/Chromosome/FRGf11FC">chromosome</a>.)

Oligomer open-in-new

Oligomer