Enhanced specificity for phosphatidylcholine analysis by positive ion mode matrix-assisted laser desorption/ionization imaging mass spectrometry

RATIONALEVisualization of the spatial distribution of phosphatidylcholine (PC) in tissues by matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI-IMS) provides insights into key physiological and pathophysiological processes. In MALDI-IMS analysis, the heterogeneity of adduct ions formed from PC lowers the specificity of detection of PC molecular species and poses a challenge in the identification of these species. To solve this problem, modified matrix solution and desalting with ammonium acetate (NH4Ac) buffer have been employed. However, the utility of these methods is limited to the analysis of brain sections. METHODSThe MALDI signal intensities of [PC+H], [PC+Na] and [PC+K] were compared after three different pretreatments (modified matrix solution, desalting with 150mM ammonium acetate, treatment with 150mM potassium acetate). RESULTSPretreatment of tissue sections with 150mM potassium acetate resulted in an increase in the signal intensity of [PC+K] ions produced from cryosections of the pancreas, brain, and liver tissues. CONCLUSIONSPretreatment with potassium acetate can be a simple, improved, and highly useful method for the reliable analysis of PC in tissues. Copyright (c) 2014 John Wiley & Sons, Ltd.