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首页> 外文期刊>Journal of mass spectrometry: JMS >The unexpected formation of [M-H]+ species during MALDI and dopant-free APPIMS analysis of novel antineoplastic curcumin analogues
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The unexpected formation of [M-H]+ species during MALDI and dopant-free APPIMS analysis of novel antineoplastic curcumin analogues

机译：新型抗肿瘤姜黄素类似物的MALDI和无掺杂APPIMS分析期间[M-H] +物种的意外形成

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摘要

Unusual ionization behavior was observed with novel antineoplastic curcumin analogues during the positive ion mode of matrixassisted laser desorption ionization (MALDI) and dopant-free atmospheric pressure photoionization (APPI). The tested compounds produced an unusual significant peak designated as [M-H]~+ ion along with the expected [M+H]~+ species. In contrast, electrospray ionization, atmospheric pressure chemical ionization and the dopant-mediated APPI (dopant-APPI) showed only the expected [M+H]~+ peak. The [M-H]~+ ion was detected with all evaluated curcumin analogues including phosphoramidates, secondary amines, amides and mixed amines/amides. Our experiments revealed that photon energy triggers the ionization of the curcumin analogues even in the absence of any ionization enhancer such as matrix, solvent or dopant. The possible mechanisms for the formation of both [M-H]~+ and [M+H]~+ ions are discussed in this paper. In particular, three proposed mechanisms for the formation of [M-H]~+ were evaluated. The first mechanism involves the loss of H_2 from the protonated [M+H]+ species. The other two mechanisms include hydrogen transfer from the analyte radical cation or hydride abstraction from the neutral analyte molecule.
机译：在基质辅助激光解吸电离（MALDI）和无掺杂剂大气压光电离（APPI）的正离子模式下，使用新型抗肿瘤姜黄素类似物观察到了异常的电离行为。被测化合物与预期的[M + H]〜+物种一起产生了一个异常的显着峰，称为[M-H]〜+离子。相反，电喷雾电离，大气压化学电离和掺杂剂介导的APPI（dopant-APPI）仅显示预期的[M + H]〜+峰。用所有评估的姜黄素类似物（包括氨基磷酸酯，仲胺，酰胺和混合的胺/酰胺）检测到[M-H]〜+离子。我们的实验表明，即使没有任何电离增强剂（例如基质，溶剂或掺杂剂），光子能量也会触发姜黄素类似物的电离。本文讨论了形成[M-H]〜+和[M + H]〜+离子的可能机理。特别地，评估了提出的三种形成[M-H]〜+的机理。第一种机制涉及质子化的[M + H] +物种损失H_2。其他两种机理包括从分析物自由基阳离子转移氢或从中性分析物分子提取氢化物。

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