Mass Spectrometry Imaging Maps Intact Proteins in Tissue

Localized liquid extraction enables high-resolution imaging of intact proteins

Category	Detail
Condition	Spatial distribution of intact proteins and proteoforms in biological tissue
Key Mechanisms	Nano-DESI extracts molecules from the tissue surface through a liquid bridge for mass spectrometry imaging; intact masses and fragmentation patterns support proteoform identification.
Target Population	Fresh-frozen tissue sections studied in proteomics research; representative imaging was performed on mouse brain tissue.
Care Setting	Laboratory-based tissue imaging and proteomics research

The protocol maps intact protein forms at approximately 10-micrometer spatial resolution.
Ethanol and chloroform washes remove lipids; ethanol also precipitates proteins to help limit their movement during delipidation.
A shear-force probe maintains probe-to-tissue distance and helps stabilize the liquid bridge while avoiding surface contact.
Multiply charged protein ions are suitable for top-down tandem mass spectrometry, and proteoforms are identified using intact masses and fragmentation patterns.
Current experiments typically detect tens of proteoforms rather than the full tissue proteome, with most reported targets being abundant proteins smaller than 20 kilodaltons.

Identify proteoforms by comparing intact masses and fragmentation patterns with database records.

Use the described workflow for research imaging of intact proteins in fresh-frozen tissue; the article does not describe clinical treatment.

Higher spatial resolution reduces the material collected at each location and can weaken protein signals.
Thicker tissue sections may make the surface less uniform and increase the risk of blocking the small capillaries.

Not applicable; the article describes a laboratory method using biological tissue, including mouse brain tissue.

No patient prescribing or treatment data are reported.

Use ethanol and chloroform washes before imaging to remove lipids that can suppress protein signals.
Maintain a constant probe-to-tissue distance with a shear-force probe to stabilize sampling and avoid capillary contact with the tissue surface.
Consider targeted tandem mass spectrometry on an adjacent tissue section after imaging identifies regions of interest.
Account for sensitivity, ionization efficiency, spectral processing, and fragmentation as areas for further method improvement.