嵌入 (化學)：修订间差异
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[[File:DNA intercalation.jpeg|thumb|300px|發生於圖中紅色區域的嵌入作用使DNA長鏈扭曲變形。]] |
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[[Image:DNA_intercalation.jpeg|thumb|right|180px|嵌入作用會使結構變形。左圖為變形前的DNA鏈；右圖為中有3個位置發生（紅色）嵌入作用]] |
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有許多分子可與生物體內的[[DNA]]發生交互作用，以[[配體 (生物化學)|配體]]為例，嵌入是配體分子與DNA的一種結合方式，當配體大小符合鹼基對之間的空隙時，就有可能發生嵌入。通常嵌入DNA的配體是多環類、芳香類，或是平面分子。常見的例子包括[[溴化乙錠]]、[[原黃素]]（proflavine）、[[道諾霉素]]（daunomycin）、[[阿黴素]]（doxorubicin）、[[沙利竇邁]]（thalidomide）等。這些物質可應用於[[化學治療]]，抑制[[癌細胞]]的生長。 |
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[[Image:DNA_intercalation2.jpg|thumb|left|250px|Ethidium intercalated between two adenine-uracyl base pairs.]] |
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There are several ways molecules - in this case, also known as "ligands" (see [[Ligand_(biochemistry)]]) - can interact with DNA. Ligands may interact with DNA by covalently binding, electrostatcially binding, or intercalating. Intercalation occurs when ligands of an appropriate size and chemical nature fit themselves in between base pairs of DNA. These ligands are mostly polycyclic, [[aromatic]], and planar, and therefore often make good nucleic acid [[staining (biology)|stains]]. Intensively studied DNA intercalators include [[ethidium]] bromide, [[proflavine]], [[daunomycin]], [[doxorubicin]], and [[thalidomide]]. DNA intercalators are used in [[chemotherapy|chemotherapeutic]] treatment to inhibit DNA replication in rapidly growing cancer cells. |
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In order for an intercalator to fit between base pairs, the DNA must dynamically open a space between its base pairs by unwinding. The degree of unwinding varies depending on the intercalator, for example, ethidium cation (the ionic form of ethidium bromide found in aqueous solution) unwinds DNA by about 26 degrees while proflavine unwinds it by about 17 degrees. This unwinding causes the base pairs to separate, or "rise", creating an opening of about 0.34 [[nanometers]] or 3.4 angstroms. This unwiding induces local structural changes to the DNA strand, such as lengthening of the DNA strand, or twisting of the base pairs. These structural modifications can lead to functional changes, often to the inhibition of [[transcription (genetics)|transcription]] and [[DNA replication|replication]] and DNA repair processes, which makes intercalators potent [[mutagen]]s. For this reason, DNA intercalators are often carcinogenic, such as the exo (but not the endo) 8,9 epoxide of [[aflatoxin]]B1, acridines such as proflavine or quinacrine, or [[ethidium bromide]]. |
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Intercalation as a mechanisim of interaction between cationic, planar, polycyclic aromatic systems of the correct size (on the order of a base pair) was first proposed by [[Leonard_Lerman]] in 1961. One proposed mechanism of intercalation is as follows: in aqueous isotonic solution, the cationic intercalator is attracted electrostatically to the polyanionic DNA. The ligand displaces a sodium and/or magnesium cation that always surround DNA (to balance its charge) and forms a weak electrostatic bond with the outer surface of DNA. From this position, the ligand may then slide into the hydrophobic environment found between the base pairs and away from the hydrophilic outer environment surrounding the DNA. The base pairs transiently form such openings due to energy absorbed during collisions with solvent molecules. |
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== 參見 == |
== 參見 == |
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* [[重疊 (化學)]] |
* [[重疊 (化學)]] |
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{{化学键和分子间作用力}} |
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[[Category:超分子化學]] |
[[Category:超分子化學]] |
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[[de:Interkalation (Chemie)]] |
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[[en:Intercalation (chemistry)]] |
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[[fr:intercalation (chimie)]] |
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[[pl:interkalacja (chemia)]] |
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2022年1月26日 (三) 05:17的最新版本
嵌入（英語：Intercalation，或譯插層）在化學上是指在兩個分子或基團之間加入一個分子，過程可逆。例如DNA嵌入與石墨层间化合物（graphite intercalation compound）。
DNA嵌入
[编辑]有許多分子可與生物體內的DNA發生交互作用，以配體為例，嵌入是配體分子與DNA的一種結合方式，當配體大小符合鹼基對之間的空隙時，就有可能發生嵌入。通常嵌入DNA的配體是多環類、芳香類，或是平面分子。常見的例子包括溴化乙錠、原黃素（proflavine）、道諾霉素（daunomycin）、阿黴素（doxorubicin）、沙利竇邁（thalidomide）等。這些物質可應用於化學治療，抑制癌細胞的生長。
