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{{refimprove|date=April 2009}} {{refimprove|date=April 2009}}
]s are often found in vapour phase.]] ]s are often found in vapour phase.]]
A '''dimer''' is a ] or ] entity consisting of two structurally similar subunits <ref>{{cite web|url=http://www.chemicool.com/definition/dimer.html | title=Definition of a dimer|accessdate=2009-04-30}}</ref> called ]s, which are held together by either ] forces (]) or weaker ] forces. A '''dimer''' is a ] or ] entity consisting of two structurally similar subunits called ]s, which are joined by bonds, which can be strong or weak.


== Chemistry == == Organic 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]] ] dimers are often formed by the reaction of two identical compounds e.g.: 2A → A-A. In this example, ] "A" is said to dimerise to give the dimer "A-A". An example is ]s, which dimerise to give ]s:
:2 C(NR<sub>2</sub>)<sub>2</sub> → (R<sub>2</sub>N)<sub>2</sub>C=C(NR<sub>2</sub>)<sub>2</sub>
] forms a dimer in the gas phase, the monomer units are held together by ]s. Under special conditions, most OH-containing molecules form dimers, e.g. the ].


] is a unsymmetrical dimer of two ] molecules have reacted to give the product. Upon heating, it "cracks" to give identical monomers:
] dimers are often formed by the reaction of two identical compounds e.g.: 2A → A-A.
:C<sub>10</sub>H<sub>12</sub> → 2 C<sub>5</sub>H<sub>6</sub>


⚫ 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 ].
In this example, ] "A" is said to dimerise to give the dimer "A-A". ]s are another example which dimerise, to give ]s.
An example of an ] or '''physical dimer''' is ] wherein ]s hold the two molecules together. The ] 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 ].


== Biochemistry == == Biochemistry ==
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=== Examples === === Examples ===
* ]s:
** ] ** ]
*]
* ]s:
** ] ** ]
** ]s:
*** ]s *** ]s
** ]s ** ]s

Revision as of 13:37, 19 August 2009

For dimers in statistical mechanics see dimer model.
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Dimers of carboxylic acids are often found in vapour phase.

A dimer is a chemical or biological entity consisting of two structurally similar subunits called monomers, which are joined by bonds, which can be strong or weak.

Organic chemistry

The dimer of cyclopentadiene although this might not be readily apparent on initial inspection

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". An example is Diaminocarbenes, which dimerise to give tetraaminoethylenes:

2 C(NR2)2 → (R2N)2C=C(NR2)2

Acetic acid forms a dimer in the gas phase, the monomer units are held together by hydrogen bonds. Under special conditions, most OH-containing molecules form dimers, e.g. the water dimer.

Dicyclopentadiene is a unsymmetrical dimer of two cyclopentadiene molecules have reacted to give the product. Upon heating, it "cracks" to give identical monomers:

C10H12 → 2 C5H6

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

See also

References

  1. "Structure-Activity Relationships of - 3'-spiro-5' '-(4' '-amino-1' ',2' '-oxathiole-2' ',2' '-dioxide)thymine Derivatives as Inhibitors of HIV-1 Reverse Transcriptase Dimerization". J. Med. Chem. 49 (16): 4834–4841. 2006. doi:10.1021/jm0604575. {{cite journal}}: Unknown parameter |authors= ignored (help)
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