Department of Chemistry, Purdue University, West Lafayette, Indiana, USA.
J Mass Spectrom. 2023 Apr;58(4):e4913. doi: 10.1002/jms.4913.
Shotgun lipid analysis using electrospray ionization tandem mass spectrometry (ESI-MS/MS) is a common approach for the identification and characterization of glycerophohspholipids GPs. ESI-MS/MS, with the aid of collision-induced dissociation (CID), enables the characterization of GP species at the headgroup and fatty acyl sum compositional levels. However, important structural features that are often present, such as carbon-carbon double bond(s) and cyclopropane ring(s), can be difficult to determine. Here, we report the use of gas-phase charge inversion reactions that, in combination with CID, allow for more detailed structural elucidation of GPs. CID of a singly deprotonated GP, [GP - H] , generates FA anions, [FA - H] . The fatty acid anions can then react with doubly charged cationic magnesium tris-phenanthroline complex, [Mg(Phen) ] , to form charge inverted complex cations of the form [FA - H + MgPhen ] . CID of the complex generates product ion spectral patterns that allow for the identification of carbon-carbon double bond position(s) as well as the sites of cyclopropyl position(s) in unsaturated lipids. This approach to determining both double bond and cyclopropane positions is demonstrated with GPs for the first time using standards and is applied to lipids extracted from Escherichia coli.
采用电喷雾串联质谱（ESI-MS/MS）的 shotgun 脂质分析是鉴定和表征甘油磷脂（GP）的常用方法。ESI-MS/MS 借助碰撞诱导解离（CID），能够在头基和脂肪酸总和组成水平上对 GP 物种进行表征。然而，通常存在的重要结构特征，如碳-碳双键和环丙烷环，可能难以确定。在这里，我们报告了使用气相电荷反转反应，该反应与 CID 结合使用，能够更详细地阐明 GP 的结构。对单脱质子的 GP [GP-H]进行 CID，生成 FA 阴离子 [FA-H]。然后，脂肪酸阴离子可以与二价阳离子镁三菲咯啉络合物 [Mg(Phen)]反应，形成形式为 [FA-H + MgPhen]的电荷反转络合阳离子。CID 生成的产物离子谱图模式可用于鉴定碳-碳双键位置以及不饱和脂质中环丙基位置。首次使用标准品，首次使用该方法来确定双键和环丙烷位置，并将其应用于从大肠杆菌中提取的脂质。
