Ceramide is a huge lipid family consisting of diversified structures in which various modifications are seen in the fatty acyl chain and the long chain base (LCB). In this contribution, a higher collision energy (HCD) linear ion-trap mass spectrometric method (LIT MSn) was applied to study the mechanisms underlying the fragmentation processes of ceramide molecules in 12 subclasses, which were desorbed by ESI as the [M + Li]+ ions. Multiple sets of fragment ions reflecting the fatty acyl chain and LCB were observed in the HCD MS2 spectra for all the ceramide classes, resulting in unambiguous definition of the ceramide structures, including the chain length and the modification (α-hydroxy-, β-hydroxy-, ω-hydroxy-FA) of the fatty acyl moiety, and the types of LCB (sphingosine, phytosphigosine, 6-hydroxy-sphingosine). Thereby, this approach permits differentiation of isomeric structures and ceramide species in the biological specimen can be unveiled in detail. By application of sequential MS3, the double bond position along the fatty acyl chain of the molecule can be located, and a complete structural characterization of ceramides can be achieved.

中文翻译：

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用高能碰撞解离串联质谱法电喷雾电离表征神经酰胺为 [M + Li]+ 离子：断裂和结构鉴定的机制

神经酰胺是一个巨大的脂质家族，由多种结构组成，其中脂肪酰基链和长链碱基 (LCB) 中存在各种修饰。在这一贡献中，应用更高碰撞能量 (HCD) 线性离子阱质谱法 (LIT MSn) 来研究 12 个亚类中神经酰胺分子裂解过程的潜在机制，这些亚类被 ESI 解吸为 [M + Li ]+ 离子。在所有神经酰胺类别的 HCD MS2 光谱中观察到多组反映脂肪酰基链和 LCB 的碎片离子，导致神经酰胺结构的明确定义，包括链长和修饰（α-羟基-，β-羟基-, ω-羟基-FA) 的脂肪酰基部分，以及 LCB 的类型（鞘氨醇、植物鞘氨醇、6-羟基-鞘氨醇）。从而，这种方法可以详细揭示生物样本中异构结构和神经酰胺种类的差异。通过应用顺序MS3，可以定位分子脂肪酰基链上的双键位置，从而实现神经酰胺的完整结构表征。