Dipole-Supported Electronic Resonances Mediate Electron-Induced Amide Bond Cleavage
Dipole-Supported Electronic Resonances Mediate Electron-Induced Amide Bond Cleavage
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DOI：
10.1103/physrevlett.122.073002
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发表时间：
2019-02-21
影响因子：
8.6
通讯作者：
Ptasinska, Sylwia
中科院分区：
文献类型：
--
作者：
Li, Zhou;Ryszka, Michal;Ptasinska, Sylwia
在高能辐射条件下，解离电子附着（DEA）在生物分子的辐射损伤中起着关键作用。DEA中的初始步骤通常被合理化为共振电子捕获到分子的亚稳价态之一，随后是其碎裂。我们结合的理论和实验研究表明，负责在DEA过程中的电子捕获的状态的歧管可以由核心激发（震动）偶极支持的共振占主导地位。具体来说，我们提出的实验和计算研究的结果的气相DEA的三个原型肽分子，甲酰胺，N-甲基甲酰胺（NMF），和N，N-二甲基甲酰胺（DMF）。与带正电荷的肽的电子捕获的情况相反，其中酰胺键断裂与N-C-α键断裂相比是罕见的，在这三种分子中的每一种中观察到酰胺键的断裂。由该酰胺键断裂产生的离子的离子产率曲线，例如甲酰胺的NH 2-、NMF的NHCH 3-和DMF的N（CH 3）（2）（-），在5和8 eV之间的区域中显示出双峰结构。峰被分配到Feshbach共振，包括核心激发的偶极支持的共振填充后，基于高层次的电子结构计算的电子附件。此外，较低的能量峰归因于与中性分子的三重态相关的核心激发共振的形成。后一个过程突出了光学自旋禁戒跃迁的作用，促进了DEA过程中的电子碰撞。
Dissociative electron attachment (DEA) plays a key role in radiation damage of biomolecules under high-energy radiation conditions. The initial step in DEA is often rationalized in terms of resonant electron capture into one of the metastable valence states of a molecule followed by its fragmentation. Our combined theoretical and experimental investigations indicate that the manifold of states responsible for electron capture in the DEA process can be dominated by core-excited (shake-up) dipole-supported resonances. Specifically, we present the results of experimental and computational studies of the gas-phase DEA to three prototypical peptide molecules, formamide, N-methylformamide (NMF), and N, N-dimethyl-formamide (DMF). In contrast to the case of electron capture by positively charged peptides in which amide bond rupture is rare compared to N-C-alpha bond cleavage, fragmentation of the amide bond was observed in each of these three molecules. The ion yield curves for ions resulting from this amide bond cleavage, such as NH2- for formamide, NHCH3- for NMF, and N(CH3)(2)(-) for DMF, showed a double-peak structure in the region between 5 and 8 eV. The peaks are assigned to Feshbach resonances including core-excited dipole-supported resonances populated upon electron attachment based on high-level electronic structure calculations. Moreover, the lower energy peak is attributed to formation of the core-excited resonance that correlates with the triplet state of the neutral molecule. The latter process highlights the role of optically spin-forbidden transitions promoted by electron impact in the DEA process.