Recent advances in matrix-assisted laser
desorption ionization (MALDI) mass spectrometry imaging (MSI) have led to the
direct analysis of tissue slices. The major advantage of MSI is its capability
of simultaneously localizing and identifying a parent molecule and its
metabolites without any labeling or any prior knowledge. MSI has beenextensively employed to detect the differentiated pattern of lipids in variousorgans in different diseases, such as brains in Alzheimer’s disease. Poor
reproducibility of MALDI MSI analysis due to the heterogeneity of the
matrix-analyte crystals, hinders its use on quantitative analysis. In addition,
discontinuous ion flow due to quickly consumption of the samples under laser
irradiation on specific site affects its ability in qualitative analysis.
Although electrospray ionization mass spectrometry (ESI-MS) cannot directly be
used for imaging, ESI tandem mass spectrometry (LC/ESI-MS/MS) can separate and
distinguish gangliosides.
Zhang et al. have presented a promising
workflow for qualitative, semi-quantitative and in situ analysis ofgangliosides by combining the MALDI MSI and ESI-MS. Following obtaining the
brain from the mice, fresh-frozen murine brain sections were prepared and
coated with matrix for subsequent MALDI MSI analysis. On the other hand, lipid
was extracted from brain tissue by Bligh and Dyer method. The gangliosides
extracts were re-suspended in water for ESI-MS analysis.
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