We have developed a novel massively parallel sample preparation strategy that allows tissue sections to be rapidly separated into single cell-sized samples for analysis using MALDI MS, termed the stretched sample method (SSM). Samples, mounted on a substrate consisting of 38-mm glass spheres embedded in Parafilm M, are stretched four-fold in each direction and then coated with a homogeneous layer of MALDI matrix. The sample is placed in a home-built temperature- and humidity-controlled chamber in order to condense water on the surface of the sample, which increases analyte extraction while inhibiting analyte redistribution and reducing salt adducts [Monroe, Int. J. Mass Spectrom. 2007]. The SSM has been used to profile the peptide content of adjacent cells in the abdominal ganglia of Aplysia californica [Monroe, Anal. Chem. 2006]. In addition, software has been developed that allows for the reconstruction of the prestretched spatial orientation of the beads, thus extending this method to image tissue samples [Zimmerman, Proteomics 2008]. Finally, enzymes have also been attached to the glass beads to provide in situ digestion sites. |
Examples of Stretched Sample Method Development |
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| A. SSM schematic demonstrating the attachment of glass beads to the membrane, stretching, and analysis. B. SSM of Aplysia californica abdominal ganglia demonstrating the ability to detect different peptide profiles from adjacent beads.
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| C. Transforming the stretched sample method into an imaging method using an algorithm to recreate the prestretched location of each bead. D. Following the attachment of trypsin to the bead, myelin digest product m/z 1849.8 was imaged using the SSM (images are 15 x 15 mm). |
Relevant Publications: E.B. Monroe, J.C. Jurchen, B.A. Koszczuk, J.L. Losh, S.S. Rubakhin, J.V. Sweedler, Massively parallel sample preparation for the MALDI MS analyses of tissues, Anal. Chem. 78, 2006, 6826-6832. T.A. Zimmerman, E.B. Monroe, J.V. Sweedler, Adapting the stretched sample method from tissue profiling to imaging, Proteomics 8, 2008, 3809-3815. |