Discussion

LESA is an ambient surface mass spectrometry approach which looks particularly promising for protein analysis. The benefits of LESA are speed of analysis, reduced sample preparation, potential for multiple sampling of the same location and, in the case of tissue sections, the potential to image multiple analytes. FAIMS is emerging as a powerful technique in biomolecular analysis. The technique relies on differences in ion mobility in high and low electric fields to achieve gas phase separation of ions at atmospheric pressure, offering advantages for peptide, protein and lipid analysis. Here, we demonstrate the coupling of LESA with FAIMS for the analysis of proteins and lipids from thin tissue sections of mouse liver and brain, and bacterial colonies growing on agar.

Incorporation of FAIMS results in significant improvements (up to four fold) 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 analysis of both sets of species from a single LESA extraction.