Matrix assisted laser desorption ionization (MALDI) mass spectrum images are created from an array of mass spectra collected over a tissue surface. We have increased the mass range of proteins that can be detected in tissue sections from kidneys, heart, lung and brain of different rodent species by a modification of the sandwich technique, which involves co-crystallizing matrix with analyte. A tissue section is placed upon a drop of sinapinic acid matrix dissolved in 90% ethanol and 0.5% Triton X-100. Once the matrix has dried, a seed layer of sinapinic crystals is added as a dispersion in xylene. Additional layers of sinapinic acid are added as solutions in 90% ethanol followed by 50% acetonitrile. Numerous peaks with signal to noise ratio of four or greater are observed between 25 kDa to 50 kDa. This represents ∼10 times as many peaks as are detected using traditional matrix spotting and spraying. © 2009 American Society for Mass Spectrometry.
Leinweber, B. D., Tsaprailis, G., Monks, T. J., & Lau, S. S. (2009). Improved MALDI-TOF Imaging Yields Increased Protein Signals at High Molecular Mass. Journal of the American Society for Mass Spectrometry, 20(1), 89–95. https://doi.org/10.1016/j.jasms.2008.09.008