Department of Chemistry, Michigan State University, East Lansing, MI, 48824, USA.
Rapid Commun Mass Spectrom. 2014 Mar 15;28(5):457-64. doi: 10.1002/rcm.6803.
Oxidized fatty acids, and particularly cyclopentenone oxylipins, are electrophilic metabolites that play diverse physiological roles. Current understanding is limited regarding how ion fragmentation provides essential information about oxylipin structures. In this work, unusual products of the collisional activation of deprotonated cyclopentenone oxylipins were investigated.
The cyclopentenone oxylipin 12-oxo-phytodienoic acid (OPDA) and its (18)O-labeled forms were ionized using negative-ion mode electrospray ionization, and product ion tandem mass (MS/MS) spectra were generated using collision-induced dissociation (CID). CID-MS/MS spectra were also generated for several cyclopentenone prostaglandins.
Upon collisional activation, deprotonated cyclopentenone oxylipins 12-oxo-phytodienoic acid (OPDA) and dinorOPDA form a characteristic and dominant product ion at m/z 165 that is attributed to charge-directed hydride migration to the electrophilic enone ring followed by elimination of neutral C7H10O2 from the carboxyl end. In contrast, pseudo-MS(3) spectra of deprotonated cyclopentenone prostaglandins exhibited a different fragmentation behavior, in that cleavage near C = C bonds is directed by the carbonyl group in the nearby cyclopentenone ring.
Two different routes of fragmentation are proposed for cyclopentenone fatty acids with saturated and unsaturated side chains. We predict that this behavior may facilitate the identification of novel cyclopentenone oxylipins and accelerate discoveries of their biological regulatory functions.
氧化脂肪酸，特别是环戊烯酮氧化脂类，是具有多种生理作用的亲电代谢物。目前对于离子碎片化如何提供关于氧化脂类结构的重要信息的理解有限。在这项工作中，研究了去质子化环戊烯酮氧化脂类的不寻常的碰撞活化产物。
使用负离子模式电喷雾电离使环戊烯酮氧化脂类 12-氧代-植物二烯酸（OPDA）及其（18）O 标记形式离子化，并使用碰撞诱导解离（CID）生成产物离子串联质谱（MS/MS）谱。还生成了几种环戊烯酮前列腺素的 CID-MS/MS 谱。
在碰撞活化时，去质子化的环戊烯酮氧化脂类 12-氧代-植物二烯酸（OPDA）和二降 OPDA 形成特征性和主要的产物离子，其质荷比（m/z）为 165，归因于电荷导向的氢迁移到亲电烯酮环，随后从羧基末端消除中性 C7H10O2。相比之下，去质子化的环戊烯酮前列腺素的伪 MS(3) 谱表现出不同的碎片化行为，即 C = C 键附近的裂解由附近环戊烯酮环中的羰基引导。
提出了具有饱和和不饱和侧链的环戊烯酮脂肪酸的两种不同的碎片化途径。我们预测，这种行为可能有助于鉴定新型环戊烯酮氧化脂类，并加速发现它们的生物调节功能。
