January 2012 Archives

C60 and Single Cells

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Castner, Ratner et al. have just published an important paper that discriminates amongst different cell types at the single cell level.  They used C60 etching to remove the overlayer junk from the lawn of cells, and principle component analysis to look for chemical differences.  The image quality was dramatically improved with the C60 treatment.  The samples were freeze-dried, and the authors acknowledge this could lead to some artifacts.  I am a bit concerned that they do not talk about the higher mass ions - in the lipid region from m/z 500-900.  It seems to me that getting these distributions at the single cell level is the holy grail of mass spec imaging right now.

Lipids and SIMS

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There is a nice review article (DOI: 10.1021/ac203126f) summarizing many of the most important techniques for characterizing phospholipid films on solid supports.  The SIMS technique gets some nice press with the following statement:

 "Imaging mass spectrometry allows label-free detection of individual sample constituents and components and area mapping of their distribution on a sample surface.  Secondary ion mass spectrometry (SIMS) is the most interesting imaging technique for phospholipid film studies, as it provides high spatial resolution on the nanometer length scale"

Unfortunately, the authors have only used nanoSIMS data to illustrate their point. There is apparently some confusion about emission of molecular ions versus atomic ions.  There is also an implication that MALDI is part of SIMS, which most people would not buy.  However, overall, the article is an interesting study that places our method in perspective.

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