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首页> 外文期刊>Journal of mass spectrometry: JMS >Fragmentation reactions of protonated alpha,omega-diamino carboxylic acids: The importance of functional group interactions
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Fragmentation reactions of protonated alpha,omega-diamino carboxylic acids: The importance of functional group interactions

机译：质子化α的碎片反应，Omega-氨基羧酸：功能群相互作用的重要性

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Protonated members of a homologous series of biologically significant alpha,omega-diamino carboxylic acids were subjected to collision induced dissociation (CID). The resulting fragmentation patterns were studied using isotopic labeling, quantum mechanical computations, and pseudo MS3 experiments conducted primarily on an ion trap mass spectrometer. Each protonated alpha,omega-diamino acid showed a primary neutral loss of either ammonia or water; a clear explanation was developed for the observed variation of the two losses within the series. Protonated 2,3-diaminopropanoic acid, 2,4-diaminobutanoic acid, and 2,7-diaminoheptanoic acid gave secondary losses of water, carbon monoxide, and a loss of water plus carbon monoxide, respectively. In the parallel pathways characterized for the fragmentations of protonated ornithine and lysine, the alpha-nitrogen of the diamino acid was maintained in the cyclic iminium product formed by successive losses of NH3 and (H2O + CO), whereas the side-chain nitrogen was retained by consecutive losses of H2O and (CO, NH3). The 1-piperideine ion from protonated lysine was fragmented further, losing ethylene from carbons 4 and 5. Protonated 2,6-diaminopimelic acid fragmented by analogous reactions. Detailed mechanistic schemes for the fragmentation of both protonated 2,3-diaminopropanoic and ornithine were generated from MP2/DFT computations. This work highlights the participation of the side-chain amino group, which distinguishes the gas-phase chemistry of protonated alpha,omega-diamino acids from the well-documented fragmentation reactions of protonated alpha-amino acids bearing a hydrogen atom or an alkyl side chain. In general, the results further illustrate the importance of intramolecular separations affecting the specific interactions between functional groups leading to the fragmentation of multifunctional ions.
机译：一系列具有重要生物学意义的α-ω-二氨基羧酸的质子化成员受到碰撞诱导解离（CID）的影响。通过同位素标记、量子力学计算和主要在离子阱质谱仪上进行的伪MS3实验，研究了由此产生的碎片模式。每一种质子化的α、ω-二氨基酸都显示出氨或水的初级中性损失；对观测到的系列内两种损失的变化给出了明确的解释。质子化的2,3-二氨基丙酸、2,4-二氨基丁酸和2,7-二氨基庚酸分别产生了水、一氧化碳和水加一氧化碳的二次损失。在以质子化鸟氨酸和赖氨酸碎裂为特征的平行路径中，二氨基酸的α氮保留在由NH3和（H2O+CO）连续损失形成的环亚胺产品中，而侧链氮则由H2O和（CO，NH3）连续损失保留。质子化赖氨酸中的1-哌啶离子进一步碎裂，从碳4和碳5中损失乙烯。通过类似反应破碎的质子化2,6-二氨基丙烯酸。通过MP2/DFT计算，生成了质子化2,3-二氨基丙酸和鸟氨酸裂解的详细机械方案。这项工作强调了侧链氨基的参与，它将质子化α、ω-二氨基酸的气相化学与文献记载的带有氢原子或烷基侧链的质子化α-氨基酸的裂解反应区分开来。总的来说，这些结果进一步说明了分子内分离的重要性，影响了导致多功能离子碎裂的官能团之间的特定相互作用。

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