Relative ion yields in mammalian cell components using C₆₀ SIMS.

Area of Science:

• Mass spectrometry
• Lipidomics
• Cell biology

Background:

• Cell membrane lipid composition influences cellular function.
• Understanding lipid-lipid interactions is crucial for cell membrane studies.
• Time of flight secondary ion mass spectrometry (ToF-SIMS) is a powerful tool for lipid analysis.

Purpose of the Study:

• To investigate the impact of molecular environment on the relative ion yields of abundant membrane lipid molecules.
• To elucidate the mechanisms behind ion suppression and enhancement in lipid mixtures.
• To simulate lipid-lipid interactions in both inner and outer leaflets of cell membranes.

Main Methods:

• Time of flight secondary ion mass spectrometry (ToF-SIMS) was employed.
• Control lipid mixtures were prepared to mimic inner and outer cell membrane leaflets.
• Proton and carbon nuclear magnetic resonance spectroscopy (¹H and ¹³C NMR) were used to investigate ion suppression mechanisms.

Main Results:

• Ion yields of 1,2-dioleoyl-sn-glycero-3-phosphocholine and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine were suppressed when mixed with 2-dipalmitoyl-sn-glycero-3-phosphocholine due to proton competition.
• NMR confirmed proton exchange and hydroxyl bond formation as mechanisms for ion suppression.
• Ion yield of 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-L-serine was enhanced in the presence of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine.

Conclusions:

• The molecular environment significantly influences the relative ion yields of membrane lipids.
• Proton exchange and lipid-lipid interactions are key factors affecting ionization efficiency in ToF-SIMS.
• These findings provide insights into lipid quantification and membrane analysis using mass spectrometry.