Laserspray Ionization, a New Atmospheric Pressure MALDI Method for Producing Highly Charged Gas-phase Ions of Peptides and Proteins Directly from Solid Solutions

The first example of a matrix-assisted laser desorption/ionization (MALDI) process producing multiply charged mass spectra nearly identical to those observed with electrospray ionization (ESI) is presented. MALDI is noted for its ability to produce singly charged ions, but in the experiments describ...

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Bibliographic Details
Published in:Molecular & cellular proteomics 2010-02, Vol.9 (2), p.362-367
Main Authors: Trimpin, Sarah, Inutan, Ellen D., Herath, Thushani N., McEwen, Charles N.
Format: Article
Language:English
Subjects:
Animals
Atmospheric Pressure
Cattle
Gases - chemistry
Ions
Muramidase
Peptides - analysis
Proteins - analysis
Solutions
Spectrometry, Mass, Electrospray Ionization
Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization - methods
Temperature
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Summary:The first example of a matrix-assisted laser desorption/ionization (MALDI) process producing multiply charged mass spectra nearly identical to those observed with electrospray ionization (ESI) is presented. MALDI is noted for its ability to produce singly charged ions, but in the experiments described here multiply charged ions are produced by laser ablation of analyte incorporated into a common MALDI matrix, 2,5-dihydroxybenzoic acid, using standard solvent-based sample preparation protocols. Laser ablation is known to produce matrix clusters in MALDI provided a threshold energy is achieved. We propose that these clusters (liquid droplets) are highly charged, and under conditions that produce sufficient matrix evaporation, ions are field-evaporated from the droplets similarly to ESI. Because of the multiple charging, advanced mass spectrometers with limited mass-to-charge range can be used for protein characterization. Thus, using an Orbitrap mass spectrometer, low femtomole quantities of proteins produce full-range mass spectra at 100,000 mass resolution with
ISSN:1535-9476
1535-9484
DOI:10.1074/mcp.M900527-MCP200