Desorption electrospray ionization (DESI) mass Spectrometry and tandem mass spectrometry (MS/MS) of phospholipids and sphingolipids: Ionization, adduct formation, and fragmentation
Desorption electrospray ionization (DESI) mass Spectrometry and tandem mass spectrometry (MS/MS) of phospholipids and sphingolipids: Ionization, adduct formation, and fragmentation
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DOI：
10.1016/j.jasms.2007.12.003
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发表时间：
2008-04-01
影响因子：
3.2
通讯作者：
Cooks, R. Graham
中科院分区：
文献类型：
--
作者：
Manicke, Nicholas E.;Wiseman, Justin M.;Cooks, R. Graham
采用解吸电喷雾电离（DESI）质谱法评价甘油磷脂标准品的表征，包括甘油胆碱（GPCho）、甘油磷酸甘油（GPGro）、甘油磷酸乙醇胺（GPEtn）、甘油磷酸丝氨酸（GPSer）、甘油磷酸肌醇（GPhis）、心磷脂（CL）和鞘脂标准品，包括硫脂；（ST）和鞘磷脂（SM）。特别感兴趣的是表面和溶剂组成对信号稳定性和强度的影响，以及在全扫描模式下观察到的离子和在碰撞激活时看到的上述每种类别的碎片。这些实验是在没有向样品中添加基质化合物的情况下进行的，并且是在大气压下的自由环境中进行的。化合物GPSer、GPGro、GPIns、ST和CL在负离子模式下分析效果最好，而PE在正离子和负离子模式下都能有效电离。SM和GPCho通常在正离子模式下产生更丰富的离子，通过在喷雾溶剂中加入醋酸盐等阴离子试剂，可以在负离子模式下进行分析。完整扫描DEST质谱和串联（MS/MS）谱为这组具有代表性的生理磷/鞘脂。尽管DEST只能对未处理样品进行环境电离，但在破碎行为方面与其他电离方法有很强的相似性。通过将标准化合物沉积在几个不同的表面上，并在水喷雾中使用不同比例的甲醇进行分析，确定了表面和溶剂性质对信号强度和稳定性的影响。通过检测猪脑的总脂质提取物和直接分析大鼠脑冷冻切片，分析扩展到磷脂和鞘脂的复杂混合物。这些类型的混合分析和分子成像研究可能是DEST应用的主要领域。
Desorption electrospray ionization (DESI) mass spectrometry was evaluated for the characterization of glycerophospholipid standards, including glycerophosphocholine (GPCho), glycerophosphoglycerol (GPGro), glycerophosphoethanolamine (GPEtn), glycerophosphoserine (GPSer), glycerophosphoinositol (GPhis), cardiolipin (CL), and sphingolipid standards, including sulfatides; (ST) and sphingomyelin (SM). Of specific interest were the effects of surface and solvent composition on signal stability and intensity, along with the ions observed in the full scan mode and the fragmentations seen upon collisional activation for each of the above classes. These experiments were performed without the addition of matrix compounds to the sample and were conducted in the free ambient environment at atmospheric pressure. The compounds GPSer, GPGro, GPIns, ST, and CL were best analyzed in the negative ion mode while PE was ionized efficiently in both positive and negative ion modes. SM and GPCho, which typically generate more abundant ions in the positive ion mode, could be analyzed in the negative ion mode by the addition of anionic reagents such as acet ate to the spray solvent. Full scan DEST mass spectra and tandem (MS/MS) spectra for this representative set of physiological phospho/sphingohpids are presented. Similarities with other ionization methods in terms of fragmentation behavior were strong, although ambient ionization of untreated samples is only available with DEST. The effect of surface and solvent properties on signal intensity and stability were determined by depositing standard compounds on several different surfaces and analyzing with various proportions of methanol in the aqueous spray. Analysis was extended to complex mixtures of phospholipids and sphingolipids by examining the total lipid extract of porcine brain and by direct analysis of rat brain cryotome sections. These types of mixture analyses and molecular imaging studies are likely to represent major areas of application of DEST.