Matrix-assisted laser desorption/ionization mass spectrometry method for selectively producing either singly or...

Area of Science:

• Analytical Chemistry
• Mass Spectrometry

Background:

• Matrix-Assisted Laser Desorption/Ionization (MALDI) typically produces singly charged ions, which is advantageous for complex mixtures but limits mass range and fragmentation analysis.
• Electrospray Ionization (ESI) generates multiply charged ions, extending mass range and aiding structural characterization, but is often less suitable for direct analysis of complex samples.

Discussion:

• A novel atmospheric pressure (AP) MALDI source with a field-free transmission geometry was designed and integrated with a high-mass resolution Orbitrap Exactive mass spectrometer.
• This AP-MALDI source enables the deliberate generation of either singly or multiply charged ions by modifying the matrix or its preparation.
• Multiply charged ion spectra comparable to ESI were achieved for proteins like cytochrome c and ubiquitin at femtomole levels and peptides like angiotensin I and II at attomole levels.

Key Insights:

• The developed AP-MALDI source offers tunable ion charge states, bridging the gap between traditional MALDI and ESI.
• High sensitivity was demonstrated, with sufficient ion current generated even from proteins in single scan acquisitions.
• This advancement expands the applicability of MALDI for analyzing large biomolecules and complex peptide mixtures.

Outlook:

• Potential for improved structural elucidation of proteins and peptides through enhanced fragmentation analysis.
• Facilitates extended mass range analysis on mass spectrometers with limited m/z capabilities.
• Opens new avenues for high-throughput analysis of complex biological and synthetic samples using MALDI-MS.