Fig. 4.

Representative 2D electrospray ionization mass spectrum of a diluted lipid extract of mouse dorsal root ganglia in the positive-ion mode. A conventional positive-ion electrospray ionization mass spectrum was acquired from a diluted mouse dorsal root ganglia lipid extract after direct infusion in the presence of LiOH. Analyses of the building blocks corresponding to glycerophosphocholine (GPCho) and galactosylceramide or galactocerebroside (GalCer) molecular species in the second dimension by neutral loss (NL) scanning were performed. ‘IS’ denotes internal standard. All mass spectral traces were displayed after normalization to the base peak in each individual spectrum.