Combining mass spectrometry, or MS, and cryogenic electron microscopy, or cryoEM, has long promised high-resolution 3D reconstructions of proteins. Past attempts were limited by low resolution and protein compaction.
3D rendering from an X-ray crystallographic study of β-galactosidase.
Keaton Mertz, Drew Jordahl and colleagues at the University of Wisconsin–Madison and the Morgridge Institute for Research developed a laser-assisted cryoEM method that overcomes these barriers, paving the way for broader MS–cryoEM integration. They published their findings in Molecular & Cellular Proteomics.
The method uses a laser built into transmission electron microscopy grids to liquefy ice particles. When the laser is turned off, proteins rehydrate and regain their native structure before refreezing, producing samples suitable for reconstruction.
Testing with β-galactosidase, the team showed that protein structure was restored without compaction. Results matched those from conventional plunge freezing but with fewer distortions. The researchers expect the technique will enable studies of more complex protein systems.