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| {{dablink|For dimers in statistical mechanics see ].}} | {{dablink|For dimers in statistical mechanics see ].}} | ||
| {{unreferenced|date=August 2006}} | {{unreferenced|date=August 2006}} | ||
| ]s are often found in vapour phase.]] | ]s are often found in vapour phase.]] | ||
| A '''dimer''' is a ] or ] entity consisting of two identical subunits <ref></ref> called ]s, which are held together by either ] forces (]) or weaker ] forces. | A '''dimer''' is a ] or ] entity consisting of two identical subunits <ref></ref> called ]s, which are held together by either ] forces (]) or weaker ] forces. | ||
| ==Chemistry== | == Chemistry == | ||
| ] although this might not be readily apparent on initial inspection]] An example of a ] dimer (i.e. held together by ] forces) is ], wherein two ] molecules have reacted to give the product. | ] although this might not be readily apparent on initial inspection]] An example of a ] dimer (i.e. held together by ] forces) is ], wherein two ] molecules have reacted to give the product. | ||
| ] dimers are often formed by the reaction of two identical compounds e.g.: 2A → A-A. | ] dimers are often formed by the reaction of two identical compounds e.g.: 2A → A-A. | ||
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| The reverse of dimerisation is often called ]. | The reverse of dimerisation is often called ]. | ||
| ==Biochemistry== | == Biochemistry == | ||
| In ] and ], dimers of ]s like ]s and ]s are often observed. The dimerization of identical subunits is called '''homodimerization'''; the dimerization of different subunits or unrelated ]s is called '''heterodimerization'''. Most dimers in biochemistry are not connected by ]s with the exception of ]s. | In ] and ], dimers of ]s like ]s and ]s are often observed. The dimerization of identical subunits is called '''homodimerization'''; the dimerization of different subunits or unrelated ]s is called '''heterodimerization'''. Most dimers in biochemistry are not connected by ]s with the exception of ]s. | ||
| An example of this would be the enzyme ], which is made of two different ] chains. | An example of this would be the enzyme ], which is made of two different ] chains. | ||
| ===Examples=== | === Examples === | ||
| * ]s: | * ]s: | ||
| ** ] | ** ] | ||
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| ** ] | ** ] | ||
| ** ] | ** ] | ||
| ** ] | ** ]ogen | ||
| ==See also== | == See also == | ||
| * ] | * ] | ||
| * ] | * ] | ||
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| * ] | * ] | ||
| == |
== References == | ||
| <references/> | |||
| == External links == | |||
| * | * | ||
| * | * | ||
Revision as of 22:50, 5 February 2009
For dimers in statistical mechanics see dimer model. | This article does not cite any sources. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Dimerization" – news · newspapers · books · scholar · JSTOR (August 2006) (Learn how and when to remove this message) |
A dimer is a chemical or biological entity consisting of two identical subunits called monomers, which are held together by either intramolecular forces (covalent bonds) or weaker intermolecular forces.
Chemistry
An example of a molecular dimer (i.e. held together by intramolecular forces) is dicyclopentadiene, wherein two cyclopentadiene molecules have reacted to give the product.
Molecular dimers are often formed by the reaction of two identical compounds e.g.: 2A → A-A.
In this example, monomer "A" is said to dimerise to give the dimer "A-A". Diaminocarbenes are another example which dimerise, to give tetraaminoethylenes.
An example of an intermolecular or physical dimer is acetic acid wherein hydrogen bonds hold the two molecules together. The water dimer is another such dimer.
The term homodimer is used when the two molecules are identical (e.g. A-A) and heterodimer when they are not (e.g. A-B).
The reverse of dimerisation is often called dissociation.
Biochemistry
In biochemistry and molecular biology, dimers of macromolecules like proteins and nucleic acids are often observed. The dimerization of identical subunits is called homodimerization; the dimerization of different subunits or unrelated monomers is called heterodimerization. Most dimers in biochemistry are not connected by covalent bonds with the exception of disulfide bridges. An example of this would be the enzyme reverse transcriptase, which is made of two different amino acid chains.
Examples
- Nucleic acids:
- DNA Polymerase
- Proteins: