文摘
The peptide content of individual mammalian cells isprofiled using matrix-assisted laser desorption/ionization(MALDI) time-of-flight mass spectrometry. Both enzymaticand nonenzymatic procedures, including a glycerol cellstabilization method, are reported for the isolation ofindividual mammalian cells in a manner compatible withMALDI MS measurements. Guided microdeposition ofMALDI matrix allows samples to be created with suitableanalyte-to-matrix ratios. More than 15 peptides are observed in individual rat intermediate pituitary cells. Thecombination of accurate mass data, expected cleavagesby proteolytic enzymes, and postsource decay sequencingallows identification of 14 of these peptides as pro-opiomelanocortin prohormone-derived molecules. Theseprotocols permit the classification of individual mammalian cells by peptide profile, the elucidation of cell-specific prohormone processing, and the discovery of newsignaling peptides on a cell-to-cell basis in a wide varietyof mammalian cell types.