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首页> 外文期刊>Journal of mass spectrometry: JMS >Evidence for site-specific intra-ionic hydrogen/deuterium exchange in the low-energy collision-induced dissociation product ion spectra of protonated small molecules generated by electrospray ionisation
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Evidence for site-specific intra-ionic hydrogen/deuterium exchange in the low-energy collision-induced dissociation product ion spectra of protonated small molecules generated by electrospray ionisation

机译：低能碰撞诱导的电喷雾电离质子化小分子的离解产物离子光谱中特定位置离子内氢/氘交换的证据

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摘要

The experimental investigation of site-specific intra-ionic hydrogen/deuterium (H/D) exchange in the low-energy collision-induced dissociation (CID) product ion spectra of protonated small molecules generated by electrospray ionisation (ESI) is presented. The observation of intra-ionic H/D exchange in such ions under low-energy CID conditions has hitherto been rarely reported. The data suggest that the intra-ionic H/D exchange takes place in a site-specific manner between the ionising deuteron, localised at either a tertiary amine or a tertiary amine-N-oxide, and a gamma-hydrogen relative to the nitrogen atom. Nuclear magnetic resonance (NMR) spectroscopy measurements showed that no H/D exchange takes place in solution, indicating that the reaction occurs in the gas phase. The compounds analysed in this study suggested that electron-withdrawing groups bonded to the carbon atom bearing the gamma-hydrogen can preclude exchange. The effect of the electron-withdrawing group appears dependent upon its electronegativity, with lower chi value groups still allowing exchange to take place. However, the limited dataset available in this study prevented robust conclusions being drawn regarding the effect of the electron-withdrawing group. The observation of site-specific intra-ionic H/D exchange has application in the area of structural elucidation, where it could be used to introduce an isotopic label into the carbon skeleton of a molecule containing specific structural features. This could increase the throughput, and minimise the cost, of such studies due to the obviation of the need to produce a deuterium-labelled analogue by synthetic means.
机译：提出了在电喷雾电离（ESI）产生的质子化小分子的低能碰撞诱导离解（CID）产物离子光谱中，进行特定位置的离子内氢/氘（H / D）交换的实验研究。迄今为止，很少有人报道在低能CID条件下观察到此类离子中的离子内H / D交换。数据表明，离子内H / D交换以位点特异性方式发生在位于氘代叔胺或叔胺-N-氧化物的离子化氘核与相对于氮原子的γ-氢之间。核磁共振（NMR）光谱测量表明，溶液中未发生H / D交换，表明反应发生在气相中。在这项研究中分析的化合物表明，结合到带有γ-氢的碳原子上的吸电子基团可以阻止交换。吸电子基团的作用似乎取决于其电负性，较低的chi值基团仍然允许交换发生。但是，这项研究中可用的数据集有限，无法得出关于吸电子基团作用的可靠结论。对位点特异性离子内H / D交换的观察已应用于结构阐明领域，可将其用于将同位素标记引入包含特定结构特征的分子的碳骨架中。由于避免了通过合成手段生产氘标记的类似物的需要，因此可以增加此类研究的通量，并使成本最小化。

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