Lipid distribution, imaging mass

Veloso A, Astigarraga E, Barreda-Gomez G, Manuel I, Ferrer I, Giralt M, Ochoa B, Fresnedo O, Rodriguez-Puertas R, Fernandez J (2011) Anatomical distribution of lipids in human brain cortex by imaging mass spectrometry. J Am Soc Mass Spectrom 22 329-338. doi 10.1007/ s 13361-010-0024-5... 

Sugiura, Y., et al. (2009) Visualization of the cell-selective distribution of PUFA-containing phosphatidylcholines in mouse brain by imaging mass spectrometry. Journal of Lipid Research, 50,1776-1788. 

Although information on the spatial distribution of membrane lipids can be important (3), most mass-spectrometric approaches used in lipidomics focus currently on the determination of total lipid composition. An advanced mass-spectrometric surface analysis technique, however, secondary ion mass spectrometry (SIMS) determines lipid compositions within different areas of freeze-fractured cells (12). This technique and related imaging techniques will become important tools in lipidomics. 

DESI is performed by directing electrosprayed-charged droplets onto a surface for analysis under atmospheric conditions. The collision of the charged droplets with the surface leads to the ionization and desorption of the analyte (35). Then, the ions produced in the gas phase are sampled by an atmospheric interfaced mass analyzer. DESI has been used to create two-dimensional images related to the distribution of lipid species in human tissues (36). 

Figure 27. Dynamical scaling of DNA confined to the surface of a supported lipid membrane, (a) Time sequence (At = 30 s) of a DNA molecule diffusing on a cationic lipid membrane. The image on the right depicts an overlay of 16 images time average yields a smeared fluorescence distribution, (b) Scaling behavior of the self-diffusion coefficient of the center of mass D with the number of base pairs, (c) Scaling behavior of the rotational relaxation time r, with the number of base pairs.140...

Eberlin, L.S., Liu, X., Ferreira, C.R., Santagata, S., Agar, N.Y., and Cooks, R.G. 2011, Desorption electrospray ionization then MALDI mass spectrometry imaging of lipid and protein distributions in single tissue sections, Anal. Chem., 15 8366-8371. 

Mass spectrometry imaging with time-of-flight secondary ion mass spectrometry (ToF-SIMS) has revealed the spatial distribution of chemicals on a surface (1). When applied to biological samples, this method offers spatial information on biologically relevant small molecules (<1,000 Da). Indeed, ToF-SIMS imaging has been shown to be a powerful analytical tool for mapping the distribution of lipids on a cell membrane at the single-cell... 

The mass spectrometric images of the various PLs in rat brain showed a remarkable variation in distribution. The use of imaging tandem MS provided a means to properly identify the ions detected and to show the many isobaric species present in the lipid mass region. In addition, it was determined that there were sometimes np to five different ions found under MALDI conditions... 

In typical DESI imaging experiments, the collected tissue sample is flash frozen in liquid nitrogen and subsequently cut in micron thin sections using a cryostat-microtome the thin tissue slices are thaw mounted onto glass microscope slides for analysis the ions generated by the DESI (Chapter 2) are transported fi om surfaces to the gas phase for mass analysis as the surface is being moved in order to cover the entire sample area a mass spectrum is acquired for each pixel on the surface and finally, tissue images are constructed to display the spatial intensity distribution of individual selected lipid ion. 

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