rMSIfragment: improving MALDI-MSI lipidomics through automated in-source fragment annotation

Identifier:  imarina:9329938

Handle: https://hdl.handle.net/20.500.11797/imarina9329938

Authors:  Baquer, G; Sementé, L; Ràfols, P; Martín-Saiz, L; Bookmeyer, C; Fernández, JA; Correig, X; García-Altares, M

Abstract:
Matrix-Assisted Laser Desorption Ionization Mass Spectrometry Imaging (MALDI-MSI) spatially resolves the chemical composition of tissues. Lipids are of particular interest, as they influence important biological processes in health and disease. However, the identification of lipids in MALDI-MSI remains a challenge due to the lack of chromatographic separation or untargeted tandem mass spectrometry. Recent studies have proposed the use of MALDI in-source fragmentation to infer structural information and aid identification. Here we present rMSIfragment, an open-source R package that exploits known adducts and fragmentation pathways to confidently annotate lipids in MALDI-MSI. The annotations are ranked using a novel score that demonstrates an area under the curve of 0.7 in ROC analyses using HPLC-MS and Target-Decoy validations. rMSIfragment applies to multiple MALDI-MSI sample types and experimental setups. Finally, we demonstrate that overlooking in-source fragments increases the number of incorrect annotations. Annotation workflows should consider in-source fragmentation tools such as rMSIfragment to increase annotation confidence and reduce the number of false positives.© 2023. Springer Nature Switzerland AG.