Rotation 1 - October - December 2019
Ion Mobility as a tool for lipidomics to understand lipid remodelling in obesity

Phd: Lipids are of fundamental importance to the cell, acting as major components of cell membranes, important energy storage sources, signalling molecules and precursors for a wide range of biomolecules. Thus, it is of fundamental importance for many biological systems to be able to measure the diverse range of lipids that make up the cellular lipidome. However, a major challenge of the mass spectrometry of complex lipid mixtures from biological material is the separation of isobaric compounds, which often have similar chromatographic properties limiting the use of liquid chromatography for separation, while fragmentation data can be inconclusive in determining chemical structure. Ion mobility allows the separation of isobaric ions based on their mobilities through an inert gas, with mobility correlated to the collisional cross sections (CCSs) of molecules. We have been applying this approach in conjunction with high resolution mass spectrometry and chromatography to maximise the resolving power of different lipid classes. As part of the method development we have also developed a data pipeline within the software package KNIME to process the three dimensional data that is produced by the workflow as well as developing an in-house database based on mass-to-charge (m/z) ratios, retention times, MS/MS spectra, and CCS values of non-labelled phospholipid and fatty acid standards. This studentship will use these developments in ion mobility based lipidomics to study diet induced obesity in a rodent model. Specifically, we will look at how diets high in saturated fats affect the composition of cell membranes within key tissues across the body, using ion mobility to increase our coverage of the lipidome. We will also investigate whether CCS values can be used to model changes in cell membrane composition and fluidity as is thought to occur when dietary saturated fats begin to displace mono- and polyunsaturated fats in cell membranes. We will combine these measurements with functional outcomes and assess mitochondrial function using oxygen electrodes, as well as lipid-induced endoplasmic reticulum and mitochondrial stress.