Mass Spectrometry Imaging
Mass spectrometry imaging (MSI) is an established analytical tool capable of defining and understanding complex tissues by determining the spatial distribution of biological molecules.
A typical MALDI imaging experiment is conducted by coating a thin tissue section mounted onto a target with an appropriate matrix solution. This solution serves to extract analytes of interest from the underlying tissue and upon solvent evaporation the extracted molecules are co-crystallized with the matrix. The role of the matrix is to absorb the laser energy and facilitate desorption/ionization of the analyte molecules. Mass spectra are then acquired across the tissue at defined geometrical coordinates. The resulting dataset contains hundreds to thousands of individual spectra consisting of all ions detected at each location of acquisition. Custom software is then used to compile the mass spectra into a format where each spectrum represents a discrete pixel and the distribution and intensity of any of the detected species can be viewed across the tissue as an ion density map or image (Figure 1) (Dong, et al., 2016; Dong, et al., 2020).
 Y. Dong et al. “More than Pictures: When MS Imaging Meets Histology”. In: Trends in Plant Science 21.8 (Aug. 2016), pp. 686-698. DOI: 10.1016/j.tplants.2016.04.007. <URL: https://doi.org/10.1016/j.tplants.2016.04.007>.
 Y. Dong et al. “High mass resolution, spatial metabolite mapping enhances the current plant gene and pathway discovery toolbox”. In: New Phytologist (Aug. 2020). DOI: 10.1111/nph.16809. <URL: https://doi.org/10.1111/nph.16809>.
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