Electrospray ionization lipid analysis

Schneiter, R. Brugger, B. Sandhoff, R. Zellnig, G. Leber, A. Lampl, M. Athenstaedt, K. Hrastnik, C. Eder, S. Daum, G. Paltauf, F. Wieland, F. T. Kohlwein, S. D. Electrospray ionization tandem mass spectrometry (ESI-MS/MS) analysis of the lipid molecular species composition of yeast subcellular membranes reveals acyl chain-based sorting/remodeling of distinct molecular species en route to the plasma membrane. J. Cell Biol. 1999,146,741-754. 

D1 (10,17S-docosatriene) from DHA using tandem liquid chromatography-photodiode array-electrospray ionization-tandem mass spectrometry (LC-PDA-ESI-MS-MS)-based lipidomic analysis have been documented in ischemic brain [4] and retinal pigment epithelium [5], This new lipid is called neuroprotectin D1 (1) because of its neuro-protectiveproperties in brain ischemia-reperfusion [4] and in oxidative stress-challenged retinal pigment epithelial cells [5] (2) because of its potent ability to inactivate proapoptotic signaling (see apoptosis, Ch. 35) [5] and (3) because it is the first identified neuroprotective mediator derived from DHA. 

A newer approach for lipid analysis is electrospray ionization tandem mass spectrometry (ESI-MS/MS) (Welti et al., 2002). This method requires limited sample preparation and sample size to identify and quantify lipids. Fauconnier et al. (2003) used ESI-MS/MS to analyze phospholipid and galactolipid levels during aging of potato tubers. 

Advanced analytical techniques, particularly mass spectrometry (MS), often combined with liquid chromatography (LC) or gas chromatography (GC), are requisite for lipid analysis and they have played the crucial role in the emergence as well as the progresses of lipidomics. MS is the principal choice for the lipid analysis, particularly using electrospray ionization (ESI) and sometimes also atmospheric pressure chemical ionization or laser-based MS methods for surface analysis. The MS-based techniques are the best choice for lipidomics due to their superior sensitivity and molecular specificity, and because they provide the ability to resolve the extensive compositional and structural diversity of lipids in biological systems. 

In recent years the rapid development of high-sensitivity analytical techniques such as mass spectrometry (MS) and liquid chromatography (LC) supported the investigation of the endocannabinoids as part of a complex lipid network. The identification of lipid components of the endocannabinoid system can be achieved in a single analytical step by state-of-the-art platforms such as tandem mass spectrometry (MS/MS), which provides the detailed structural information necessary for characterization of lipids and increases specificity in complex biological matrices. Furthermore, the implementation of ionization techniques such as electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) allow the coupling of LC to MS, and permits the separation and analysis of endocannabinoids with greater speed and accuracy. 

Electrospray mass spectrometry has developed into a well-established method of wide scope and potential over the past 15 years. The softness of electrospray ionization has made this technique an indispensable tool for biochemical and biomedical research. Electrospray ionization has revolutionized the analysis of labile biopolymers, with applications ranging from the analysis of DNA, RNA, oligonucleotides, proteins as well as glycoproteins to carbohydrates, lipids, gly-colipids, and lipopolysaccharides, often in combination with state-of-the-art separation techniques like liquid chromatography or capillary electrophoresis [1,2]. Beyond mere analytical applications, electrospray ionization mass spectrometry (ESMS) has proven to be a powerful tool for collision-induced dissociation (CID) and multiple-stage mass spectrometric (MSn) analysis, and - beyond the elucidation of primary structures - even for the study of noncovalent macromolecular complexes [3]. 

Analytical methods for tocol analysis have continued to improve, as noted by Abidi (2000), and in the intervening ten years, as noted in this chapter. We predict that advances will continue to be made in the field of the chromatographic analysis of tocols. Also, we believe that lipidomic methods (quantitative analysis via direct injection tandem electrospray ionization mass spectrometry) will be developed for the rapid analysis of tocols, just as these methods have already been used for the profiling of phospholipids and glycolipids (Han, 2011 Welti, 2011). These methods usually involve the direct injection of lipid samples into a... 

The dynamic development of mass spectrometry has had a huge impact on lipid analysis. Currently, a variety of suitable mass spectrometers is available. In principal, a mass spectrometer consists of an ion source, a mass analyzer, and an ion detector. The typical features of each instrument (Fig. 2) result mostly from the types of ion source and mass analyzer. To date, the ionization techniques apphed to lipid analysis include Electrospray Ionization (ESI or nano-ESI), Atmospheric Pressure Chemical Ionization (APCI), Matrix-Assisted Laser Desorption/Ionization... 

Brtigger B, Erben G, Sandhoff R, Wieland FT, Lehmann WD. Quantitative analysis of biological membrane lipids at the low picomole level by nano electrospray ionization tandem mass spectrometry. Proc. Natl. Acad. Sci. U.S.A. 1997 94 2339-2344. 

Cai SS, Syage JA. Comparison of atmospheric pressure photoionization, atmospheric pressure chemical ionization, and electrospray ionization mass spectrometry for analysis of lipids. Anal. Chem. 2006 78 1191-1199. 

Nearly all known ionization methods of mass spectrometry (including electron impact, laser desorption and fast atom bombardment) were already successfully applied to lipids. However, many ionization techniques are not very suitable for the analysis of complex PL mixtures as they provide considerable amounts of fragment ions. Therefore, only three soft-ionization methods play nowadays a major role in lipid analysis. Beside atmospheric pressure chemical ionization (APCI) (Byrdwell 2001), electrospray ionization (ESI) (Pulfer and Murphy... 

Figure 9.2 The basic components of a mass spectrometer. All mass spectrometers consist of an ion source linked to a mass analyser then to a detector. The important ion sources and mass analysers for biological mass spectrometry are listed. There are many other potential ion sources and mass analysers used generally in mass spectrometry, but only the indicated are of use in the analysis of biological macromolecules and amphiphilic lipids, and also in proteomics FAB fast atom bombardment MALDI matrix-assisted laser desorption and ionization ESI electrospray ionization ToF time of flight FTICR fourier transform ion cyclotron resonance MS/MS tandem mass spectrometry.

Thermospray and, more recently, electrospray ionization have found wide application as an interface technology between HPLC instruments and mass spectrometers. They represent powerful techniques for the analysis of complex lipids directly from solutions (Henion and Lee, 1990 Murphy, 1993). In most instances, the total HPLC eluant can be sent directly into the heated thermospray ion source. Here, the combination of heat and eluant velocity creates a plume of small-diameter particles suspended in a vapor (nebulization). A strong electric charge forms on the surface of the liquid particles and as the droplets evaporate the increase in charge ionizes analyte molecules that are discharged directly from the droplet into the gas phase. From here, they may enter the mass spectrometer directly. 

One of the most powerful techniques used in Upid analysis today is HPLC coupled with mass spectrometry (HPLC/MS). Several mass spectrometric ionization techniques, such as fast atom bombardment (FAB) [23], electrospray ionization (ESI) [29,30], ionspray ionization (ISI) [31], and atmospheric pressure chemical ionization (APCI) [22,30,32] have been used. By using HPLC/MS, one can get information on the molecular structure of the intact lipids, which helps differentiate molecular species within different lipid classes. By using tandem mass spectrometry (MS/MS), identification of molecular species of different sphingolipids can be achieved in an easier and more sensitive way. There are many other advantages of using MS, such as small sample size, minimal sample preparation, and lack of need for derivatization, speeds, and sensitivity. In the literature, sphingolipids of both animal and plant origin were analyzed by MS. 

Figure 2.10 Reconstructed MRM traces for Bligh/Dyer extract of sterols from mouse brain. Known sterols are labeled, unknown compounds with a sterollike signature are indicated by . MS/MS of the respective steroids can be found at Lipid Maps http //www.lipidmaps.org/data/standards/standards. php lipidclass=LMST. (Reproduced with permission from McDonald, J. G. et al., 2007, Extraction and Analysis of Sterols in Biological Matrices by High-Performance Liquid Chromatography Electrospray Ionization Mass Spectrometry, Methods Enzymol. 432 145-70.)...

Pike, L. J., X. Han, K. N. Chung, and R. W. Gross. 2002. Lipid rafts are enriched in ara-chidonic acid and plasmenylethanolamine and their composition is independent of caveohn-l expression A quantitative electrospray ionization/mass spectrometric analysis, 41 2075-88. 

Sjovall, O. and Kuksis, A. (1997a) Analysis of oxidized triacylglycerols by LC/MS with electrospray ionization. I. Hydroperoxides, hydroxides, and epoxides. Lipids, submitted. 

Paglia, G Ifa, D.R., Wu, C Corso, G., Cooks, R.G. (2010) Desorption Electrospray Ionization Mass Spectrometry Analysis of Lipids after Two-dimensional High-Performance Thin-Layer Chromatography Partial Separation. Anal. Chem. 82 ... 

Han, X., Gross, R.W (2001) Quantitative analysis and molecular species fingerprinting of triacylglyceride molecular species directly from lipid extracts of biological samples by electrospray ionization tandem mass spectrometry. Analytical Biochemistry, 295, 88-100. 

Features of Electrospray Ionization for lipid Analysis In addition to intrasource separation for lipid analysis, there exist numerous other features of ESI for lipid analysis as follows ... 

Hsu, E.-E. and Turk, J. (2005) Electrospray ionization with low-energy collisionally activated dissociation tandem mass spectrometry of complex lipids Structural characterization and mechaiusm of fragmentation. In Modern Methods for Lipid Analysis by Liquid Chromatography/Mass Spectrometry and Related Techiuques (Byrdwell, W.C., ed.). pp. 61-178, AOCS Press, Champaign, IL. 

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