For proteins to be analyzed by mass spectrometry (MS), they must first be ionized. Electrospray ionization (ESI) produces multiple charged ions from proteins in solution that can be analyzed on high-accuracy mass spectrometers. Matrix-assisted laser desorption/ionization (MALDI) MS permits molecular imaging of solid biological materials. But both methods have drawbacks: MALDI needs high voltage, which limits the size of protein complexes one can look at, and ESI requires that proteins be in solution. Inutan and Trimpin now take the best of both methods and show that soft ionization can be achieved directly by exposing solid biological material in a matrix to vacuum. The researchers applied this 'matrix-assisted ionization vacuum' method to fragile molecules and large molecular complexes.
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Soft ionization with vacuum alone. Nat Methods 10, 105 (2013). https://doi.org/10.1038/nmeth.2346
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DOI: https://doi.org/10.1038/nmeth.2346
