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首页> 外文期刊>Chemistry: A European journal >Expanding the horizon of the thymine Isostere biochemistry: Unique cyclobutane dimers formed by photoreaction between a thymine and a toluene residue in the dinucleotide framework
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Expanding the horizon of the thymine Isostere biochemistry: Unique cyclobutane dimers formed by photoreaction between a thymine and a toluene residue in the dinucleotide framework

机译：拓宽胸腺嘧啶等位基因生物化学的视野：独特的环丁烷二聚体是由胸腺嘧啶和二核苷酸框架中的甲苯残基之间的光反应形成的

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摘要

Substituted toluenyl groups are considered as close isosteres of the thymine residue. They can be recognized by DNA polymerases as if they were thymine. These toluene derivatives are generally inert toward radical additions, including the [2+2] photocycloadditions, due to the stable structure of the aromatic ring and are usually used as solvents for radical reactions. Surprisingly, after incorporating toluene into the dinucleotide framework, we found that the UV excited thymine residue readily dimerizes with the toluenyl moiety through a [2+2] photoaddition reaction. Furthermore, the reaction site on the toluenyl moiety is not the C5=C6 bond, as commonly observed in cyclobutane pyrimidine dimers, but the C4=C5 or C3=C4 instead. Such a reaction pattern suggests that in the stacked structure, it is one of these bonds, not the C5=C6, that is close to the thymine C5=C6 bond. A similar structural feature is found in DNA duplex with a thymine replaced by a 2,4-difluorotoluene. Our results argue that although the substituted toluenyl moieties closely mimic the size and shape of the thymine residue, their more hydrophobic nature determines that they stack on DNA bases differently from the natural thymine residue and likely cause local conformational changes in duplex DNA.
机译：取代的甲苯基被认为是胸腺嘧啶残基的紧密等排体。它们可以被DNA聚合酶识别，就好像它们是胸腺嘧啶一样。由于芳环的稳定结构，这些甲苯衍生物通常对包括[2 + 2]光环加成在内的自由基加成是惰性的，通常用作自由基反应的溶剂。出乎意料的是，在将甲苯掺入二核苷酸骨架中之后，我们发现紫外线激发的胸腺嘧啶残基易于通过[2 + 2]光加成反应与甲苯基部分二聚。此外，甲苯基团部分上的反应位点不是如在环丁烷嘧啶二聚体中通常观察到的C5 = C6键，而是C4 = C5或C3 = C4。这种反应模式表明，在堆叠结构中，接近胸腺嘧啶C5 = C6的键是这些键之一，而不是C5 = C6。在DNA双链体中发现了类似的结构特征，其中胸腺嘧啶被2,4-二氟甲苯取代。我们的结果认为，尽管取代的甲苯基部分与胸腺嘧啶残基的大小和形状非常相似，但它们的疏水性决定了它们在DNA碱基上的堆叠方式与天然胸腺嘧啶残基不同，并可能导致双链体DNA发生局部构象变化。

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