Combining Charge-Switch Derivatization with Ozone-Induced Dissociation for Fatty Acid Analysis

Area of Science:

• Lipidomics
• Mass Spectrometry
• Organic Chemistry

Background:

• Unsaturated fatty acid double bond positions critically influence lipid properties and biological roles.
• Current mass spectrometry methods struggle to pinpoint unsaturation sites in fatty acids.
• Accurate determination of fatty acid structure is essential for understanding metabolic pathways.

Purpose of the Study:

• To develop a novel workflow for unambiguous determination of carbon-carbon double bond locations in fatty acids.
• To enhance the detection and structural elucidation of fatty acyl lipids using mass spectrometry.
• To profile the complex fatty acid unsaturation patterns in biological samples like vernix caseosa.

Main Methods:

• Fatty acids are derivatized to form fixed charge N-(4-aminomethylphenyl)pyridinium (AMPP) derivatives.
• Ozone-induced dissociation (OzID) is employed on a modified triple quadrupole mass spectrometer for fragmentation.
• A data-dependent workflow combines collision-induced dissociation (CID) with OzID for automated analysis.

Main Results:

• The AMPP derivatization enhances direct infusion detection of fatty acids.
• Diagnostic CID fragments aid in triggering targeted OzID analyses.
• OzID provides unambiguous assignment of double bond locations in AMPP-derivatized fatty acids.
• Analysis of vernix caseosa revealed significant isomeric diversity and novel double bond positional isomers.

Conclusions:

• The developed workflow enables precise localization of double bonds in unsaturated fatty acids.
• This method significantly advances the structural analysis capabilities in lipidomics.
• The findings in vernix caseosa suggest the existence of previously unknown metabolic pathways.