Abstract

How to Maximize the Structural Output from the Mass Spectrometer? Using Different Fragmentation Approaches for Annotation and Identification of Small Molecules

Justin van der Hooft, Postdoctoral Research Associate, University of Glasgow

Metabolite annotation and identification remains the primary challenge in untargeted mass spectrometry approaches [1]. Without rigorous metabolite annotation and identification tools, the output of any comparative untargeted study will remain a list of statistically significantly different masses and their corresponding retention times. This study explores the use of different fragmentation approaches for the structurally very diverse metabolites in biological extracts. In the proteomics field, this has been performed for peptide annotation and fragmentation [2]. Here, a diverse range of metabolite standards relevant for Glasgow Polyomics and extracts of human urine were subjected to multistage MS fragmentation (using collision induced dissociation – CID [3,4]) and MS/MS fragmentation (using higher-energy collision dissociation -HCD). Fragmentation spectra so obtained were compared and the effectiveness of the fragmentation approaches was evaluated. We used a combination of specific fragments and neutral losses to generate effective filters to screen for specific classes of metabolites. For example, acylcarnitines are a diverse group of metabolites that have been associated as biomarkers for cancer and diabetes, and were used as markers during newborn screening. Our approach allowed the annotation of more than 50 acylcarnitines species in human urine, sixteen of which have not been previously reported and annotated in this biofluid.