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自由基的离解生成质子、亲电试剂或亲核试剂:在 DNA 链断裂中的作用。

Dissociations of free radicals to generate protons, electrophiles or nucleophiles: role in DNA strand breaks.

机构信息

EaStCHEM School of Chemistry, University of St. Andrews, St. Andrews, Fife KY16 9ST, UK.

出版信息

Chem Soc Rev. 2021 Jul 5;50(13):7496-7512. doi: 10.1039/d1cs00193k.

Abstract

The concept behind the research described in this article was that of marrying the 'soft' methods of radical generation with the effectiveness and flexibility of nucleophile/electrophile synthetic procedures. Classic studies with pulse radiolysis and laser flash photolysis had shown that free radicals could be more acidic than their closed shell counterparts. QM computations harmonised with this and helped to define which radical centres and which structural types were most effective. Radicals based on the sulfonic acid moiety and on the Meldrum's acid moiety (2,2-dimethyl-1,3-dioxane-4,6-dione) were found to be extreme examples in the superacid class. The ethyne unit could be used as a very effective spacer between the radical centre and the site of proton donation. The key factor in promoting acidity was understood to be the thermodynamic stabilisation of the conjugate anion-radicals released on deprotonation. Solvation played a key part in promoting this and theoretical microhydration studies provided notable support. A corollary was that heterolytic dissociations of free radicals to yield either electrophiles or nucleophiles were also enhanced relative to non-radical models. The most effective radical types for spontaneous releases of both these types of reagents were identified. Ethyne units were again effective as spacers. The enhancement of release of phosphate anions by adjacent radical centres was an important special case. Reactive oxygen species and also diradicals from endiyne antibiotics generate C4'-deoxyribose radicals from nucleotides. Radicals of these types spontaneously release phosphate and triphosphate and this is a contributor to DNA and RNA strand breaks.

摘要

本文所述研究的理念是将自由基的“软”生成方法与亲核/亲电合成程序的有效性和灵活性相结合。使用脉冲辐射分解和激光闪光光解的经典研究表明,自由基可以比其闭合壳层对应物更具酸性。QM 计算与这一结果一致,并有助于确定哪些自由基中心和结构类型最有效。基于磺酸部分和 Meldrum 酸部分(2,2-二甲基-1,3-二氧戊环-4,6-二酮)的自由基被发现是超强酸类中的极端例子。乙炔单元可用作自由基中心和质子供体位置之间的非常有效的间隔基。促进酸度的关键因素是脱质子化释放的共轭阴离子-自由基的热力学稳定化。溶剂化在促进这一点方面起着关键作用,理论微观水合研究提供了显著的支持。推论是,自由基的异裂解离产生亲电试剂或亲核试剂也相对于非自由基模型得到增强。确定了最有效的自由基类型,用于自发释放这两种类型的试剂。乙炔单元再次作为间隔基有效。相邻自由基中心对磷酸根阴离子释放的增强是一个重要的特殊情况。活性氧物质和来自 endiyne 抗生素的双自由基从核苷酸中生成 C4'-脱氧核糖自由基。这些类型的自由基自发释放磷酸盐和三磷酸盐,这是 DNA 和 RNA 链断裂的一个贡献者。

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