Sensitivity is generally an issue in bioassays of prostaglandins and their synthetic analogs due to their extremely low concentration in vivo. To improve the ionization efficiency of limaprost, an oral prostaglandin E1 (PGE1) synthetic analog, we investigated a charge reversal derivatization strategy in electrospray ionization mass spectrometry (ESI-MS). We established that the cholamine derivative exhibits much greater signal intensity in the positive-ion mode compared with limaprost in the negative ion mode. Collision-induced dissociation (CID) involved exclusive neutral mass loss and positive charge migration to form stable cationic product ions with the positive charge on the limaprost residue rather than on the modifying group. This has the effect of maintaining the efficiency and specificity of multiple reaction monitoring (MRM) and avoiding cross talk. CID fragmentation patterns of other limaprost derivatives allowed us to relate the dissociation tendency of different neutral leaving groups to an internal energy distribution scale based on the survival yield method. Knowledge of the energy involved in the production of stabilized positive ions will potentially assist the selection of suitable derivatization reagents for the analysis of a wide variety of lipid acids.

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由于前列腺素及其合成类似物在体内的浓度极低，因此敏感性在前列腺素及其合成类似物的生物测定中通常是一个问题。。为提高口服前列腺素E1（PGE1）合成类似物利马前列素的电离效率，我们研究了电喷雾电离质谱（ESI-MS）中的电荷逆转衍生化策略。我们确定，与利马前列素在负离子模式下相比，胆碱衍生物在正离子模式下表现出更大的信号强度。碰撞诱导解离（CID）涉及排他性中性质量损失和正电荷迁移，以形成稳定的阳离子产物离子，在利马前列素残基而不是修饰基团上带有正电荷。这具有保持多反应监测（MRM）的效率和特异性并避免串扰的效果。其他利马前列素衍生物的CID碎裂模式使我们能够基于存活率法将不同的中性离去基团的解离趋势与内部能量分布尺度相关联。了解产生稳定的阳离子所需的能量将可能有助于选择合适的衍生化试剂，以分析各种脂质酸。

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