Liquid micro-junction surface sampling and MALDI imaging of small and large molecules in human liver disease

In this thesis, Liquid extraction surface analysis (LESA) mass spectrometry has been applied for the analysis of lipids and proteins from human liver. The aim was to develop analytical methods that would ultimately be used in the study of non-alcoholic liver disease. Top-down proteomic analysis of the fatty acid binding protein identified a single amino acid substitution that is associated with non-alcoholic steatohepatitis, a potentially fatal liver disease. Bottom-up proteomics techniques resulted in over 300 proteins being detected and identified, however failed to distinguish between a single amino acid substitution. Field asymmetric ion mobility spectrometry (FAIMS) analysis was coupled with LESA to enhance the quality of intact protein mass spectra and doubled the number of proteins detected. FAIMS analysis was able to separated lipids and proteins that were extracted simultaneously as well as removing background noise. In addition to FAIMS, traveling wave ion mobility spectrometry (TWIMS) was also coupled to LESA. In addition to the separation of lipids from proteins, several lipids also showed a separation in drift. MS/MS of one of these lipids revealed that the composition of the two drift peaks differed. MALDI imaging was performed to show the isolation of specific lipid species using MS/MS and TWIMS