Abstract
Previously we have shown that liquid extraction surface analysis (LESA) mass spectrometry is suitable for the analysis of intact proteins from a range of biological substrates. Here we show that LESA mass spectrometry may be coupled with high field asymmetric waveform ion mobility spectrometry (FAIMS) for top-down protein analysis directly from thin tissue sections (mouse liver, mouse brain) and from bacterial colonies (Escherichia coli) growing on agar. Incorporation of FAIMS results in significant improvements in signal-to-noise and reduced analysis time. Abundant protein signals are observed in single scan mass spectra. In addition, FAIMS enables gas-phase separation of molecular classes, for example, lipids and proteins, enabling improved analysis of both sets of species from a single LESA extraction.
Highlights
Previously we have shown that liquid extraction surface analysis (LESA) mass spectrometry is suitable for the analysis of intact proteins from a range of biological substrates
LESA field asymmetric waveform ion mobility spectrometry (FAIMS) analyses were performed on thin tissue sections from mouse liver and mouse brain and on E. coli colonies growing on agar (Note, the analysis of bacteria made use of the “contact” LESA approach described in ref 7)
LESA FAIMS mass spectrometry analyses, in which both the dispersion field (DF) and the compensation field (CF) were varied (2D FAIMS analysis), were performed on thin tissue sections from mouse liver and mouse brain and on E. coli growing on agar
Summary
The miniaturized chip-based ultraFAIMS device was coupled with the orbitrap mass spectrometer and the Triversa Nanomate, see Supporting Information, Figure 1. Similar results were obtained following LESA FAIMS analysis of mouse brain and E. coli, see Supporting Information, Figures 3 and 4. The total ion transmission maps obtained following LESA 2D-FAIMS MS analyses of mouse brain and E. coli are shown in Supporting Information, Figure 6. Similar trends were observed in both cases As discussed, this particular mouse brain sample is dominated by the presence of an unknown protein of ∼22 kDa, and this feature is apparent in the total ion transmission maps. This protein has not previously been identified following LESA of E. coli colonies
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