Improved MALDI-TOF Imaging Yields Increased Protein Signals at High Molecular Mass

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.

Graphical AbstractMALDI imaging mass spectrometry creates images of proteins in tissue sections. Sandwiching tissue sections between layers of matrix improves the signal from 20 to 50 kDa proteins.Figure optionsDownload high-quality image (148 K)Download as PowerPoint slide