Molecular profiling of native and matrix-coated tissue slices from rat brain by infrared and ultraviolet laser desorption/ionization orthogonal time-of-flight mass spectrometry.

Phospho- and glycolipids contained in the plasma membrane of neuronal tissue were profiled by direct infrared laser desorption/ionization orthogonal time-of-flight mass spectrometry (IR-LDI-o-TOF-MS), performed on cryosected native slices generated from rat brain. About 100 different detected lipid species are putatively assigned based on their molecular weight. Spraying of potassium acetate onto the slices was found to facilitate data interpretation in positive ion mode by reducing residual sodium adduct ion intensities. Coating the slices with matrix and using an ultraviolet laser for UV-MALDI-o-TOF-MS extends the analysis to peptides and small proteins but induces analyte diffusion. Peptides and partially cleaved proteins derived from proteolytic digests were recorded after incubation of native sections with trypsin and subsequent coating of the slices with MALDI matrix.