MS Imaging

In Situ Top Down Proteomics: Targeted Imaging of Proteins in Tissue Using Laser Ablation Electrospray Ionization Mass Spectrometry (LAESI-MS)

Top down proteomics and identification of intact proteins from biological tissues have been among the most challenging aspects of mass spectrometry imaging. Highly abundant endogenous proteins have been detected previously by laser ablation electrospray ionization (LAESI-MS) and targeted top-down proteomics LAESI-FT-ICR methodologies directly from tissue have been reported previously.

In this work, we report the use of LAESI-MS to perform targeted MS and MS/MS analyses on endogenous proteins directly ablated from frozen animal tissue section with minimal sample preparation. In LAESI-MS, frozen tissues are ablated with a mid-infrared laser (2.94μm) at ambient pressure to form a plume of neutrals that are intercepted by electrospray to ionize the sample prior to introduction into the mass spectrometer (Figure 1). We also employed a more traditional LC-MS analysis workflow to confirm the presence of endogenous histones in the washed tissue homogenate.

[presented at ASMS 2015]





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