Radical Cascade Dissociation Pathways to Unusual Nucleobase Cation Radicals
Radical Cascade Dissociation Pathways to Unusual Nucleobase Cation Radicals
复制标题
异常核碱基阳离子自由基的自由基级联解离途径
DOI：
10.1021/jasms.2c00098
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发表时间：
2022
影响因子：
3.2
通讯作者：
Tureček, František
中科院分区：
文献类型：
--
作者：
Zima, Václav;Liu, Yue;Tureček, František
我们报道了在核糖5′-O上标记自由基引发基团并带有2′，3 ′-O-异亚丙基保护基的质子化RNA核苷的不寻常解离。离子经历从自由基引发剂开始的碰撞诱导的自由基级联解离，其破坏二氧戊环环并触发核碱基阳离子和阳离子自由基的形成。由自由基级联解离形成的腺嘌呤阳离子自由基经MS 5 UV-vis光解离作用光谱鉴定为典型电离核碱基的高能N-3-H互变异构体。鸟嘌呤阳离子自由基通过自由基级联解离形成N-7-H互变异构体。与腺苷和鸟苷相反，标记的核糖胞苷离子的自由基级联解离产生质子化胞嘧啶，而标记的核糖胸苷显示出不同的解离，导致主要的胸腺嘧啶损失。级联解离的反应机制是基于玻恩-奥本海默分子动力学和密度泛函理论计算，被用来映射腺苷，鸟苷，和胞苷自由基离子的势能面的相关部分。报道的自由基级联解离代表了一种新的，nonredox方法的核碱基和核苷阳离子自由基，有可能被扩大到各种寡核苷酸阳离子自由基的产生。
We report unusual dissociations of protonated RNA nucleosides tagged with radical initiator groups at ribose 5′-O and furnished with a 2′,3′-O-isopropylidene protecting group. The ions undergo collision-induced radical cascade dissociations starting at the radical initiator that break down the dioxolane ring and trigger the formation of nucleobase cations and cation radicals. The adenine cation radical that was formed by radical cascade dissociations was identified by MS5UV–vis photodissociation action spectroscopy to be a higher-energy N-3-H tautomer of the canonical ionized nucleobase. The guanine cation radical was formed by radical cascade dissociations as the N-7-H tautomer. In contrast to adenosine and guanosine, radical cascade dissociations of the tagged ribocytidine ion produced protonated cytosine, whereas tagged ribothymidine showed yet different dissociations resulting in predominant thymine loss. Reaction mechanisms were suggested for the cascade dissociations that were based on Born–Oppenheimer molecular dynamics and density functional theory calculations that were used to map the relevant parts of the potential energy surfaces for adenosine, guanosine, and cytidine radical ions. The reported radical cascade dissociations represent a new, nonredox approach to nucleobase and nucleoside cation radicals that has the potential of being expanded to the generation of various oligonucleotide cation radicals.