Direct identification of proteins from T47D cells and murine brain tissue by matrix‐assisted laser desorption/ionization post‐source decay/collision‐induced dissociation

The purpose of this study is to determine the feasibility of the direct matrix‐assisted laser desorption/ionization (MALDI) identification of proteins in fixed T47D breast cancer cells and murine brain tissues. The ability to identify proteins from cells and tissue may lead to biomarkers that effectively predict the onset of defined disease states, and their dynamic behavior could be an important hint for drug target discoveries. Direct tissue application of trypsin allows protein identification in cells and tissues, while maintaining spatial integrity and intracellular organization. Using a chemical printer, matrix was co‐registered on trypsinized human T47D breast cancer cells and cryo‐preserved sections of murine brain tissue, followed by MALDI post‐source decay (PSD) or MALDI collision‐induced dissociation (CID), respectively. Mass‐to‐charge (m/z) data from the cells and brain tissues were processed using Mascot© software interrogation of the National Center for Biotechnology Information (NCBI) database. Histone H2B was identified from cultured T47D human breast cancer cells. Tubulin β2 was identified from mouse brain cortex following an induced stroke. These results suggest that MALDI PSD/CID, combined with bioinformatics, can be used for the direct identification of proteins from cells and tissues. Refinements in preparation techniques may improve this approach to provide a tool for quantitative proteomics and clinical analysis. Copyright © 2007 John Wiley & Sons, Ltd.