Adapting the stretched sample method from tissue profiling to imaging. Proteomics

Department of Chemistry, Beckman Institute, University of Illinois, Urbana, IL 61801, USA.
Proteomics (Impact Factor: 3.81). 09/2008; 8(18):3809-15. DOI: 10.1002/pmic.200800331
Source: PubMed


The characterization and localization of peptides and proteins in tissues provides information that aids in understanding their function and in characterizing disease states. Over the past decades, the use of MS for the profiling and imaging of biological compounds from tissues has evolved into a powerful modality to accomplish these studies. One recently described sampling approach, the stretched sample method (Monroe, E. B. et al.., Anal. Chem. 2006, 78, 6826-6832), places a tissue section onto an array of glass beads embedded on a Parafilm M membrane. When the membrane is stretched, it separates the tissue section into thousands of cell-sized pieces for tissue profiling by MALDI-MS. The physical separation between beads eliminates analyte redistribution during matrix application and allows long analyte extraction periods without loss of spatial resolution. Here, we enhance this sampling approach by introducing algorithms that enable the reconstruction of ion images from these stretched samples. As the first step, a sample-tailored data acquisition method is devised to obtain mass spectra exclusively from the beads, thereby reducing the time, instrument resources, and data handling required for such MS imaging (MSI) experiments. Next, an image reconstruction algorithm matches data acquired from the stretched sample to the initial bead locations. The efficacy of this method is demonstrated using peptide-coated beads with known peptide distributions and appears well-suited to the MSI of heterogeneous tissue samples.

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    • "The traditional approach uses thaw-mounting of the tissue slice on a conductive microscope glass coated with indium-tin oxide (ITO) to assure the conductivity. Another approach uses glass bead embed in parafilm to stretch the landed tissue slice, in order to increase the spatial resolution (Zimmerman et al. 2008). Samples may require further treatment such as selective washing and enzymatic digestion, and must undergo deposition of MALDI matrix for MS analysis. "
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