School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, Brisbane, QLD, 4000, Australia.
Central Analytical Research Facility, Institute for Future Environments, Queensland University of Technology, Brisbane, QLD, 4000, Australia.
Rapid Commun Mass Spectrom. 2020 May 15;34(9):e8741. doi: 10.1002/rcm.8741.
Eicosanoids are short-lived bio-responsive lipids produced locally from oxidation of polyunsaturated fatty acids (FAs) via a cascade of enzymatic or free radical reactions. Alterations in the composition and concentration of eicosanoids are indicative of inflammation responses and there is strong interest in developing analytical methods for the sensitive and selective detection of these lipids in biological mixtures. Most eicosanoids are hydroxy FAs (HFAs), which present a particular analytical challenge due to the presence of regioisomers arising from differing locations of hydroxylation and unsaturation within their structures.
In this study, the recently developed derivatization reagent 1-(3-(aminomethyl)-4-iodophenyl)pyridin-1-ium (4-I-AMPP ) was applied to a representative set of HFAs including bioactive eicosanoids. Photodissociation (PD) mass spectra obtained at 266 nm of 4-I-AMPP -modified HFAs exhibit abundant product ions arising from photolysis of the aryl-iodide bond within the derivative with subsequent migration of the radical to the hydroxyl group promoting fragmentation of the FA chain and facilitating structural assignment.
Representative polyunsaturated HFAs (from the hydroxyeicosatetraenoic acid and hydroxyeicosapentaenoic acid families) were derivatized with 4-I-AMPP and subjected to a reversed-phase liquid chromatography workflow that afforded chromatographic resolution of isomers in conjunction with structurally diagnostic PD mass spectra.
PD of these complex HFAs was found to be sensitive to the locations of hydroxyl groups and carbon-carbon double bonds, which are structural properties strongly associated with the biosynthetic origins of these lipid mediators.
类二十烷酸是短寿命的生物响应脂质，通过酶促或自由基反应级联从多不饱和脂肪酸 (FA) 的氧化中局部产生。类二十烷酸的组成和浓度的改变表明炎症反应，并且人们强烈关注开发用于在生物混合物中灵敏和选择性检测这些脂质的分析方法。大多数类二十烷酸是羟基脂肪酸 (HFA)，由于其结构中羟化和不饱和位置的不同，存在区域异构体，这给分析带来了特殊的挑战。
在这项研究中，最近开发的衍生试剂 1-(3-(氨甲基)-4-碘苯基)吡啶-1- 翁 (4-I-AMPP) 被应用于一组代表性的 HFA，包括生物活性类二十烷酸。在 266nm 处获得的 4-I-AMPP 修饰的 HFA 的光解 (PD) 质谱显示，大量的产物离子源于衍生剂中芳基-碘键的光解，随后自由基迁移到羟基，促进 FA 链的断裂，并促进结构鉴定。
代表性的多不饱和 HFA（来自羟二十碳四烯酸和羟二十碳五烯酸家族）与 4-I-AMPP 衍生化，并进行反相液相色谱工作流程，与异构体的色谱分离相结合，同时获得结构诊断 PD 质谱。
发现这些复杂 HFA 的 PD 对羟基和碳-碳双键的位置敏感，这些结构特性与这些脂质介质的生物合成起源密切相关。
