Kerwin J L, Torvik J J
Department of Botany 351330, University of Washington, Seattle, Washington, 98195, USA.
Anal Biochem. 1996 May 15;237(1):56-64. doi: 10.1006/abio.1996.0200.
Negative-ion electrospray mass spectrometry (ESI-MS) and tandem mass spectrometry (ESI-MS/MS) were used to characterize saturated and unsaturated monohydroxy fatty acids and fatty acid metabolites formed following incubation with soybean lipoxygenase. Ions corresponding to [M-H]- of eicosanoids were readily observed using ESI-MS, but double bond migration precluded the use of MS to localize double bonds or the position of hydroxyl moieties; however, by following MS analysis with negative-ion ESI-MS/MS of precursor ions, the position of oxygenation could be determined for picogram quantities of underivatized monohydroxy fatty acids. Loss of 46 mass units from the precursor ion of saturated monohydroxy compounds was explained in some cases by resonance stabilization of enolate ions, but this product ion was found in spectra of compounds where resonance was not possible. Spectra of deuterated analogs supported charge-driven vinylic processes as the most common mechanism of fragmentation. The utility of low-collision-energy ESI-MS/MS to examine biological samples was shown by examining the products formed by the metabolism of linoleic (18:2omega6) and arachidonic (20:4omega6) acids by soybean lipoxygenase using aerobic and anaerobic incubation conditions that generated increasingly complex mixes of metabolites.
负离子电喷雾质谱（ESI-MS）和串联质谱（ESI-MS/MS）用于表征饱和与不饱和单羟基脂肪酸以及与大豆脂氧合酶孵育后形成的脂肪酸代谢产物。使用ESI-MS很容易观察到类二十烷酸对应于[M-H]-的离子，但双键迁移使得无法使用质谱来确定双键的位置或羟基部分的位置；然而，通过对前体离子进行负离子ESI-MS/MS分析，可以确定皮克级未衍生化单羟基脂肪酸的氧化位置。在某些情况下，饱和单羟基化合物前体离子损失46个质量单位可通过烯醇负离子的共振稳定来解释，但在无法发生共振的化合物光谱中也发现了该产物离子。氘代类似物的光谱支持电荷驱动的乙烯基过程是最常见的裂解机制。通过在需氧和厌氧孵育条件下研究大豆脂氧合酶对亚油酸（18:2ω6）和花生四烯酸（20:4ω6）的代谢产物，展示了低碰撞能量ESI-MS/MS在检测生物样品方面的实用性，这些条件会产生越来越复杂的代谢产物混合物。
