Internal energy build-up in matrix-assisted laser desorption/ionization

Area of Science:

• Analytical Chemistry
• Mass Spectrometry
• Physical Chemistry

Background:

• Matrix-assisted laser desorption/ionization (MALDI) is a key technique for analyzing large biomolecules.
• Understanding ion internal energy is crucial for interpreting fragmentation patterns in MALDI mass spectrometry.
• Previous studies have identified multiple sources of internal energy in MALDI ions, but their contributions are complex to disentangle.

Purpose of the Study:

• To investigate the origins and contributions of internal energy build-up in ions formed by MALDI.
• To compare fragmentation patterns and ion internal energy in vacuum-MALDI and atmospheric pressure MALDI (AP-MALDI).
• To utilize benzylpyridinium cations as probes for internal energy studies.

Main Methods:

• Utilized delayed extraction MALDI-time-of-flight (TOF) mass spectrometry.
• Employed atmospheric pressure (AP) MALDI mass spectrometry.
• Analyzed benzylpyridinium cations as internal energy probes.

Main Results:

• Identified three distinct contributions to internal energy in vacuum-MALDI ions: prompt fragmentation (thermal and chemical activation) and extraction-induced collisional activation.
• Observed that prompt fragmentation occurs within 100 ns of laser impact.
• Found that AP-MALDI eliminates extraction-induced fragmentation and improves reproducibility, isolating early plume activation events.

Conclusions:

• AP-MALDI is advantageous for studying early fragmentation events due to the absence of extraction-induced fragmentation and enhanced reproducibility.
• The findings provide new insights into the fundamental processes governing ion internal energy in MALDI.
• Further research using AP-MALDI can elucidate the initial steps of the MALDI ionization process.