We investigated the product ion spectra of [M + Na]+ from diterpene diester species and low molecular mass metabolites analyzed by electrospray ionization (ESI). Mainly, the formation of protonated salt structures was proposed to explain the observed neutral losses of carboxylic acids. It also facilitates understanding sodium retention on product ions or on neutral losses. In addition, the occurrence of consecutive carboxylic acid losses is rather unexpected under resonant excitation conditions. Quantum calculation demonstrated that the exothermic character of such neutral losses can represent a relevant explanation. There is no doubt that the formation and role of the protonated salt structures will be helpful for a better understanding and software-assisted interpretation of tandem mass spectra from small molecules, especially in the ever-growing metabolomics field.

中文翻译：

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结合化学知识和量子计算来解释代谢物加合物离子的低能产物离子光谱：以钠化二萜二酯物种为例。

我们研究了通过电喷雾电离 (ESI) 分析的二萜二酯物种和低分子量代谢物的 [M + Na]+ 的产物离子光谱。主要是提出质子化盐结构的形成来解释观察到的羧酸的中性损失。它还有助于了解产物离子或中性损失的钠保留。此外，在共振激发条件下，连续羧酸损失的发生是相当出乎意料的。量子计算表明，这种中性损失的放热特性可以代表相关的解释。毫无疑问，质子化盐结构的形成和作用将有助于更好地理解和软件辅助解释小分子的串联质谱，