Robert Jansen (@robertsjansen.bsky.social)

Large-scale discovery and annotation of hidden substructure patterns in mass spectrometry profiles Untargeted mass spectrometry measures many spectra of unknown molecules. Tandem mass spectrometry (MS/MS) generates fragmentation patterns representing common substructures termed Mass2Motifs. However, MS/MS-based substructure identification is limited by computational efficiency and interpretability. Here, we introduce a complete overhaul of MS2LDA, overcoming limitations of its predecessor. We report an up to 14x speed improvement for unsupervised Mass2Motif discovery, allowing it to process larger datasets. Furthermore, the new automated Mass2Motif Annotation Guidance (MAG) aids in structurally identifying Mass2Motifs. Using three curated MotifDB-MotifSets for benchmarking, MAG achieved median substructure overlap scores of 0.75, 0.93, and 0.95. On experimental data, we validated MS2LDA 2.0 by identifying substructures of pesticides spiked into a biological matrix and demonstrated its discovery potential by annotating previously uncharacterized fungal natural products. Together with the new visualization app and MassQL-searchable MotifDB, we anticipate that MS2LDA 2.0 will boost the identification of novel chemistry and hidden patterns in mass spectrometry. http://dlvr.it/TLTKwd