Visible-Light Paternò–Büchi Reaction for Lipidomic Profiling at Detailed Structure Levels

The Paternò–Büchi (PB) derivatization of carbon–carbon double bond (CC) has been increasingly employed with tandem mass spectrometry to analyze unsaturated lipids. It enables the discovery of altered or uncanonical lipid desaturation metabolism, which would be otherwise undetected by conventional methods. Although highly useful, the reported PB reactions only provide moderate yield (∼30%). Herein, we aim to determine the key factors that affect the PB reactions and develop a system with improved capabilities for lipidomic analysis. An Ir­(III) photocatalyst is chosen as the triplet energy donor for the PB reagent under 405 nm light irradiation, while phenylglyoxalate and its charge-tagging version, pyridylglyoxalate, are developed as the most efficient PB reagents. The above visible-light PB reaction system provides higher PB conversions than all previously reported PB reactions. Around 90% conversion can be achieved at high concentrations (>0.5 mM) for different classes of lipids but drops as the lipid concentration decreases. The visible-light PB reaction has then been integrated with shotgun and liquid chromatography-based workflows. The limits of detection for locating CC in standard lipids of glycerophospholipids (GPLs) and triacylglycerides (TGs) are in the sub-nM to nM range. More than 600 distinct GPLs and TGs have been profiled at the CC location level or the sn-position level from the total lipid extract of bovine liver, demonstrating that the developed method is capable of large-scale lipidomic analysis.碳-碳双键（C=C）的帕特诺-布奇（Paternò–Büchi，PB）衍生化技术愈发频繁地与串联质谱（tandem mass spectrometry）联用，用于不饱和脂质的分析。该方法可揭示传统方法无法检测到的脂质去饱和代谢异常或非经典代谢通路。尽管该反应应用价值显著，但已报道的PB反应产率仅为中等水平（约30%）。 本研究旨在明确影响PB反应的关键因素，并开发一套性能更优的脂质组学分析体系。我们选用铱(III)光催化剂作为405 nm光照下PB试剂的三重态能量供体，同时开发出苯乙醛酸酯及其电荷标记衍生物吡啶乙醛酸酯作为迄今最高效的PB试剂。上述可见光驱动PB反应体系的PB转化率优于所有此前已报道的PB反应。在浓度高于0.5 mM的高浓度条件下，不同类别脂质的转化率可达约90%，但随脂质浓度降低而出现下降。 随后，该可见光PB反应被整合至鸟枪法脂质组学及液相色谱联用分析流程中。针对甘油磷脂（glycerophospholipids，GPLs）与三酰甘油（triacylglycerides，TGs）标准品中C=C位点的检测限处于亚纳摩尔至纳摩尔级别。从牛肝总脂质提取物中，我们已完成超过600种不同甘油磷脂和三酰甘油的C=C位点或sn位（立体特异性编号位）层面的表征分析，证实所开发的方法可实现大规模脂质组学分析。