Subtle Changes in Lipid Environment Have Profound Effects on Membrane Oxidation Chemistry

Area of Science:

• Biophysical chemistry
• Surface chemistry
• Lipidomics

Background:

• Amphiphile-composed membranes exhibit delicate structures crucial for function.
• Physical properties of membranes are well-studied, but associated chemical properties are less understood.
• Understanding lipid chemistry is vital for predicting membrane behavior.

Purpose of the Study:

• To investigate the impact of lipid packing on the chemical properties of membrane amphiphiles.
• To explore the OH-mediated oxidation pathways of unsaturated lipids and surfactants at the air-water interface.
• To elucidate the role of molecular packing in controlling reaction mechanisms and products.

Main Methods:

• Utilized field-induced droplet ionization mass spectrometry (FIDI-MS) for analysis.
• Studied six different unsaturated lipids/surfactants and their mixtures.
• Analyzed reactions at the air-water interface under varying packing conditions.

Main Results:

• Observed distinct oxidation pathways based on lipid packing density.
• Loose packing led to oxygen addition without double bond cleavage.
• Compact packing resulted in double bond cleavage, suggesting a Criegee intermediate mechanism.

Conclusions:

• Lipid packing is a critical determinant of chemical reactivity in amphiphile membranes.
• Constrained environments influence reaction intermediate conformations, thereby controlling chemical pathways.
• This study provides the first examples of delicate chemistry governing membrane amphiphilic components.