Direct Tissue Profiling of Protein Complexes: Toward Native Mass Spectrometry Imaging

Native mass spectrometry seeks to probe noncovalent protein interactions in terms of protein quaternary structure, protein–protein and protein–ligand complexes. The ultimate goal is to link the understanding of protein interactions to the protein environment by visualizing the spatial distribution of noncovalent protein interactions within tissue. Previously, we have shown that noncovalently bound protein complexes can be directly probed via liquid extraction surface analysis from dried blood spot samples, where hemoglobin is highly abundant. Here, we show that the intact hemoglobin complex can be sampled directly from thin tissue sections of mouse liver and correlated to a visible vascular feature, paving the way for native mass spectrometry imaging.