Matrix-assisted laser desorption/ionization (MALDI) mechanism revisited

Area of Science:

• Analytical Chemistry
• Mass Spectrometry
• Biochemistry

Background:

• Matrix-assisted laser desorption/ionization (MALDI) is a widely used technique for analyzing biomolecules.
• The precise ionization mechanism in MALDI remains incompletely understood.
• Existing photochemical ionization (PI) and cluster ionization (CI) models do not fully explain all experimental observations.

Purpose of the Study:

• To propose a novel mechanism for analyte ion formation in MALDI.
• To explain the simultaneous production of positive and negative ions for large biomolecules.
• To compare the proposed model with existing MALDI ionization mechanisms.

Main Methods:

• Development of the energy transfer induced disproportionation (ETID) model.
• Theoretical consideration of a pseudo proton transfer process during crystallization.
• Comparison of the ETID model with PI and CI models using experimental data.

Main Results:

• The ETID model provides a framework for understanding analyte ion generation in MALDI.
• The model accounts for the observation of equimolar positive and negative ion formation for large biomolecules.
• The ETID model offers a potential explanation for phenomena not covered by PI and CI mechanisms.

Conclusions:

• A pseudo proton transfer during crystallization is proposed as a primary ion formation mechanism in MALDI.
• The energy transfer induced disproportionation (ETID) model offers a new perspective on MALDI ionization.
• Further experimental validation is needed to fully establish the ETID model's applicability.