Collision-induced dissociation of homodimeric and heterodimeric radical cations of 9-methylguanine and 9-methyl-8-oxoguanine: correlation between intra-base pair proton transfer originating from the N1–H at a Watson–Crick edge and non-statistical dissocia
Collision-induced dissociation of homodimeric and heterodimeric radical cations of 9-methylguanine and 9-methyl-8-oxoguanine: correlation between intra-base pair proton transfer originating from the N1–H at a Watson–Crick edge and non-statistical dissocia
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9-甲基鸟嘌呤和 9-甲基-8-氧代鸟嘌呤的同二聚体和异二聚体自由基阳离子的碰撞诱导解离：源自 Watson–Crick 边缘 N1–H 的碱基对内质子转移与非统计解离之间的相关性
DOI：
10.1039/d2cp00312k
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发表时间：
2022
影响因子：
3.3
通讯作者：
Liu, Jianbo
中科院分区：
文献类型：
--
作者：
Moe, May Myat;Benny, Jonathan;Liu, Jianbo
先前在质子化、去质子化和电离的鸟嘌呤-胞嘧啶碱基对中已经表明，碱基对内质子从鸟嘌呤的沃森-克里克边缘的h1 - h转移到互补的核碱基上会引起碱基对系统的非统计解离，并且质子转移的碱基对结构的解离比起始的常规碱基对结构的解离更有利。然而，这种异常和有趣的动力学背后的基本化学尚未完全揭示，这需要在不同的结构背景下检查更多的碱基对系统，以得出广义的碱基对结构-动力学相关性。本研究的目的是将研究范围扩大到9-甲基鸟嘌呤（9MG）和9-甲基-8-氧鸟嘌呤（9MOG）的非规范同二聚体和异二聚体自由基阳离子，即[9MG·9MG]˙+、[9MOG·9MG]˙+和[9MOG·9MOG]˙+。实验上，采用碰撞诱导离解串联质谱联用电喷雾电离（ESI）源对碱基对自由基阳离子的形成进行了研究，随后检测了在单离子-分子碰撞条件下与Xe气体碰撞时的离解产物离子和横截面以及质心碰撞能量的函数。在计算上，采用密度泛函理论和耦合簇理论计算并确定可能的碱基对结构和碱基对内质子转移和氢转移反应，然后通过动力学建模来探索解离过渡态的性质和动力学因素。这项工作的意义是双重的：它提供了在氧化和电离损伤的三个生物学上重要的非规范系统中碱基对打开动力学的见解；它将非统计解离与8-氧鸟嘌呤Watson-Crick边缘N1-H产生的碱基对内质子转移联系起来，增强了对质子转移辅助碱基对断裂的理解。
It has been shown previously in protonated, deprotonated and ionized guanine–cytosine base pairs that intra-base pair proton transfer from the N1–H at the Watson–Crick edge of guanine to the complementary nucleobase prompts non-statistical dissociation of the base-pair system, and the dissociation of a proton-transferred base-pair structure is kinetically more favored than that of the starting, conventional base-pair structure. However, the fundamental chemistry underlying this anomalous and intriguing kinetics has not been completely revealed, which warrants the examination of more base-pair systems in different structural contexts in order to derive a generalized base-pair structure–kinetics correlation. The purpose of the present work is to expand the investigation to the non-canonical homodimeric and heterodimeric radical cations of 9-methylguanine (9MG) and 9-methyl-8-oxoguanine (9MOG), i.e., [9MG·9MG]˙+, [9MOG·9MG]˙+ and [9MOG·9MOG]˙+. Experimentally, collision-induced dissociation tandem mass spectrometry coupled with an electrospray ionization (ESI) source was used for the formation of base-pair radical cations, followed by detection of dissociation product ions and cross sections in the collisions with Xe gas under single ion–molecule collision conditions and as a function of the center-of-mass collision energy. Computationally, density functional theory and coupled cluster theory were used to calculate and identify probable base-pair structures and intra-base pair proton transfer and hydrogen transfer reactions, followed by kinetics modeling to explore the properties of dissociation transition states and kinetic factors. The significance of this work is twofold: it provides insight into base-pair opening kinetics in three biologically-important, non-canonical systems upon oxidative and ionization damage; and it links non-statistical dissociation to intra-base pair proton-transfer originating from the N1–H at the Watson–Crick edge of 8-oxoguanine, enhancing understanding towards the base-pair fragmentation assisted by proton transfer.