Pulse Duration Effects on Solution-Phase Protein Desorption in Laser Electrospray Mass Spectrometry.

Area of Science:

• Analytical Chemistry
• Biophysics
• Mass Spectrometry

Background:

• Laser electrospray mass spectrometry (LEMS) is a technique used for analyzing biomolecules.
• Understanding laser-induced effects on biomolecules is crucial for optimizing analytical methods.

Purpose of the Study:

• To investigate the impact of varying laser pulse durations on the ablation of aqueous myoglobin.
• To quantify laser-induced thermal effects and their influence on protein conformation.

Main Methods:

• Aqueous myoglobin was ablated from stainless-steel and quartz substrates using femtosecond (fs), picosecond (ps), and nanosecond (ns) laser pulses.
• Laser electrospray mass spectrometry (LEMS) was employed to analyze the ablated samples.
• Heat-induced conformation changes were assessed by analyzing solvent and phosphate adduction, baseline elevation, and the ratio of unfolded to folded myoglobin.

Main Results:

• Myoglobin signal intensity increased with decreasing laser pulse duration for both substrates.
• Femtosecond (55 fs) pulses showed significant solvent and phosphate adduction and baseline elevation compared to nanosecond (10 ns) pulses.
• Femtosecond ablation resulted in a higher ratio of unfolded to folded myoglobin due to increased droplet lifetime, but this could be mitigated by reducing droplet lifetime.

Conclusions:

• Laser pulse duration significantly affects the ablation efficiency and thermal effects on myoglobin during LEMS.
• Femtosecond laser pulses, while causing some thermal effects, can preserve protein conformation more effectively than longer pulses when droplet lifetime is controlled.
• Optimizing laser pulse duration and experimental conditions in LEMS is key to minimizing thermal damage and preserving biomolecular integrity.