Mapping of surrogate markers of cellular components and structures using laser desorption/ionization mass spectrometry

Laser desorption/ionization mass spectrometry (LDI-MS) has been used to ass ess the potential of using surrogate markers, bound to cellular structures containing nucleic acids, to image or map the position of these structures within biological samples. In this study, organic dyes were used as markers because of their established use in the histochemical marking of nucleic a cids, and also because they are amenable to LBI-MS. Eight cationic dyes wer e tested and ail could be desorbed from nucleic acid samples without additi onal matrix after specifically binding to these molecules, Methylene Blue w as the best of these based on its sensitivity to detection by LDI-MS and th e fact that it can be washed from the tissue in areas where it was not spec ifically bound to provide low-intensity background signals, Experiments are reported which characterize the M+ ion signal obtained from Methylene Blue with regard to sensitivity, reproducibility and possible use for quantitat ion, This dye was used to map (with a lateral resolution of 25 mu m) severa l nucleic acid-containing samples spotted on prepared surfaces, and to imag e the location of nucleic acids in two model tissues, retinal vertical sect ions and thyroid whole mount sections. Copyright (C) 2000 John Wiley & Sons , Ltd.