Imaging mass spectrometry of intact proteins from alcohol-preserved tissue specimens: bypassing formalin fixation.

Imaging mass spectrometry is becoming a key technology for the investigation of the molecular content of biological tissue sections in direct correlation with the underlying histology. Much of our work has been done with fresh-frozen tissue sections that has undergone minimal protein degradation between the time a tissue biopsy is sampled and the time it is snap-frozen so that no preserving or fixing agents need to be added to the frozen biopsy. However, in many sampling environments, immediate flash freezing may not be possible and so we have explored the use of ethanol-preserved, paraffin-embedded tissue specimens for proteomic analyses. Solvent-only preserved tissue specimens provide long-term preservation at room temperature, generation of high quality histological sections and little if any chemical alteration of the proteins. Using mouse organs, several key steps involved in the tissue dehydration process have been investigated to assess the potential of such preserved specimens for profiling and imaging mass spectrometry investigations.