Thermal desorption effects on fragment ion production from multi-photon ionized uridine and selected analogues.
Thermal desorption effects on fragment ion production from multi-photon ionized uridine and selected analogues.
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作者：
中性气相核苷的实验常常因热不稳定性而变得复杂。先前的核苷质谱研究已经确定，解吸温度作为热分解的关键指标，增强了核碱基离子（例如尿嘧啶生成尿嘧啶+）的相对生成。在此基础上，本文的多光子电离（MPI）实验表明，基于激光的热解吸可以有效地制备尿嘧啶、5-甲基尿嘧啶和2 ' -脱氧尿嘧啶靶标，而不需要热分解。我们的实验还揭示了一个显著的热依赖性：完整尿苷的糖离子C5H9O4+的相对产量随着解吸激光功率的增加而显著增加，这只发生在MPI波长低于250 nm（全范围研究了222-265 nm）。我们认为，这种影响只能合理地在不同的异构体，互变异构体，或构象的变化种群的目标作为一个函数的热解吸条件。此外，这种热敏MPI通道的波长阈值行为表明，第一光子和第二光子吸收之间的中性激发态动力学至关重要。实验结果与密度泛函数理论（DFT）优化的尿苷最低能量结构和分子糖部分羟甲基不同取向的两个构象相相补充。与分解所需的能量相比，这三种构象之间的过渡态能量较低。这项工作揭示了第一个实验证据支持同分异构体依赖于辐射反应的核苷。
Experiments on neutral gas-phase nucleosides are often complicated by thermal lability. Previous mass spectrometry studies of nucleosides have identified enhanced relative production of nucleobase ions (e.g. uracil+ from uridine) as a function of desorption temperature to be the critical indicator of thermal decomposition. On this basis, the present multi-photon ionization (MPI) experiments demonstrate that laser-based thermal desorption is effective for producing uridine, 5-methyluridine, and 2′-deoxyuridine targets without thermal decomposition. Our experiments also revealed one notable thermal dependence: the relative production of the sugar ion C5H9O4+ from intact uridine increased substantially with the desorption laser power and this only occurred at MPI wavelengths below 250 nm (full range studied 222–265 nm). We argue that this effect can only be rationalized plausibly in terms of changing populations of different isomers, tautomers, or conformers in the target as a function of the thermal desorption conditions. Furthermore, the wavelength threshold behavior of this thermally-sensitive MPI channel indicates a critical dependence on neutral excited state dynamics between the absorption of the first and second photons. The experimental results are complemented by density functional theory (DFT) optimizations of the lowest-energy structure of uridine and two further conformers distinguished by different orientations of the hydroxymethyl group on the sugar part of the molecule. The energies of the transitions states between these three conformers are low compared with the energy required for decomposition. This work reveals the first experimental evidence supporting isomer-dependence in the radiation response of a nucleoside.
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在气相中分离的核苷尿苷。
DOI：
10.1002/anie.201412460
发表时间：
2015-03-02
期刊：
Angewandte Chemie (International ed. in English)
影响因子：
--
作者：
Peña I;Cabezas C;Alonso JL
通讯作者：
Alonso JL
影响因子：
8.6
作者：
Maclot, S.;Delaunay, R.;Rousseau, P.
通讯作者：
Rousseau, P.
影响因子：
2.9
作者：
Nachtigallova, Dana;Aquino, Adelia J. A.;Lischka, Hans
通讯作者：
Lischka, Hans
影响因子：
2.2
作者：
Delchev, Vassil B.
通讯作者：
Delchev, Vassil B.
影响因子：
7.4
作者：
Huang, Zhipeng;Ossenbrueggen, Tim;Kuepper, Jochen
通讯作者：
Kuepper, Jochen