| abstract |
MALDI MS has been used to generate images of samples in one or more m/z pictures, providing the capability of mapping concentrations of specific molecules in X,Y coordinates of the original sample. For sections of mammalian tissue, for example, this can be accomplished in two ways. First, tissue slices can be directly analyzed after thorough drying and application of a thin coating of matrix by electrospray. Second, imprints of the tissue can be analyzed by blotting the dry tissue sections on specially prepared targets, e.g., C-18 (10 mu m dia.) beads. Peptides and small proteins bind to the C-18 and create a positive imprint of the tissue which can be imaged by MALDI MS after application of matrix. Such images can be displayed in individual m/z values as a selected ion image which would localize individual compounds in the tissue, as summed ion images, or as a total ion image which would be analogous to a photomicrograph. This imaging process may also be applied to separation techniques where a physical track or other X,Y deposition process is utilized, for example, in the CE/MALDI MS combination where a track is deposited on a membrane target. |