Nanoparticle-Assisted Cation Adduction and Fragmentation of Small Metabolites.

Mass spectrometry (MS) promises small-metabolite profiling as a tool of the future and calls for the comprehensive understanding of key procedures to enhance its capability. Herein, we studied cation adduction and fragmentation of small metabolites by a combination of theoretical and experimental approaches, via nanoparticle-assisted laser desorption/ionization (LDI)-MS and MS/MS. We calculated the energies of adduction conformers and atomic bond orders to establish the rules of cation-metabolite affinity and multiple cation adductions in charge transfer. Further, we demonstrated the reaction paths of adducted ions and mapped the potential energy surfaces to characterize the loss of given groups during fragmentation. Finally, we successfully controlled metabolite fragmentation by selected and multiple adductions to enhance the atomic/fragment coverage as defined for metabolite identification toward profiling. Considering the success of MS in the analysis of large biomolecules, our work may have an impact and guide to advanced analysis of small metabolites.