Surface analysis of lipids by mass spectrometry: More than just imaging

Abstract

Mass spectrometry is now an indispensable tool for lipid analysis and is arguably the driving force in the renaissance of lipid research. In its various forms, mass spectrometry is uniquely capable of resolving the extensive compositional and structural diversity of lipids in biological systems. Furthermore, it provides the ability to accurately quantify molecular-level changes in lipid populations associated with changes in metabolism and environment; bringing lipid science to the "omics" age. The recent explosion of mass spectrometry-based surface analysis techniques is fuelling further expansion of the lipidomics field. This is evidenced by the numerous papers published on the subject of mass spectrometric imaging of lipids in recent years. While imaging mass spectrometry provides new and exciting possibilities, it is but one of the many opportunities direct surface analysis offers the lipid researcher. In this review we describe the current state-ofthe-art in the direct surface analysis of lipids with a focus on tissue sections, intact cells and thin-layer chromatography substrates. The suitability of these different approaches towards analysis of the major lipid classes along with their current and potential applications in the field of lipid analysis are evaluated. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 2 AbstractMass spectrometry is now an indispensable tool for lipid analysis and is arguably the driving force in the renaissance of lipid research. In its various forms, mass spectrometry is uniquely capable of resolving the extensive compositional and structural diversity of lipids in biological systems. Furthermore, it provides the ability to accurately quantify molecular-level changes in lipid populations associated with changes in metabolism and environment;bringing lipid science to the "omics" age. The recent explosion of mass spectrometry-based surface analysis techniques is fuelling further expansion of the lipidomics field. This is evidenced by the numerous papers published on the subject of mass spectrometric imaging of lipids in recent years. While imaging mass spectrometry provides new and exciting possibilities, it is but one of the many opportunities direct surface analysis offers the lipid researcher. In this review we describe the current state-of-the-art in the direct surface analysis of lipids with a focus on tissue sections, intact cells and thin-layer chromatography substrates.The suitability of these different approaches towards analysis of the major lipid classes along with their current and potential applications in the field of lip...

A Comparison of DESI-MS and LC-MS for the Lipidomic Profiling of Human Cancer Tissue

“…Therefore difference will not exist due to varying adduct formation but rather the spectral features that define that sample. Similar patterns of metal adduct formation have previously been identified in MALDI lipidomic experiments, highlighting the challenges of comparative analysis and absolute lipid quantification [29,30].…”

“…Nevertheless, if the signal from a lipid is split over three mass channels as is the case with methanol:water solvents in positive ion mode, the signal-to-noise for that lipid could be worse even if the overall signal is better in the absence of a dopant. The use of a dopant to mitigate the problem of metal adducts formation in positive ion mode DESI-MS has been previously described in a study using sodium acetate [30,33]. In addition, washing the tissue sample with ammonium acetate prior to analysis has been shown to desalt the sample, remove contaminants, and improve spectral quality in MALDI-MS experiments [34].…”

Differential Lipid Profiles in Experimental Steatohepatitis: Role for Imaging Mass Spectrometry as a Diagnostic Aid

“…Examples of glycerophospholipids found in biological membranes are phosphatidylcholine (also known as PC), phosphatidylethanolamine (PE), phosphatidylinositol (PI), and phosphatidylserine (PS). MALDI-IMS has been used extensively to study lipids in tissue because IMS can resolve their structures and compositional diversity [32,33]. For example, MALDI-IMS has been used to visualize the heterogeneous distribution of PC species in mouse brains [34], and effects of traumatic brain injury on the differential localization of PCs in rat brains [35].…”

Lipidomics

“…Desorption techniques are also used for tissue imaging to determine the spatial distribution of lipid species. 20 2. Electrospray-ionization is a low-energy ionization (softionization) technique, and the most common method for lipid characterization because of its minimal in-source fragmentation.…”