biostudies-literatureChen YNational Natural Science Foundation of China1320-1324https://www.ebi.ac.uk/biostudies/studies/S-EPMC9627732biostudies-literatureUnknown3(11)Post-translational modifications (PTMs) play important roles in modulating the biological functions of proteins. Stoichiometry, which quantifies the modification percentage, is a critical factor for any given PTM. In this work, we developed a chemoproteomic strategy called "STO-MS" to systematically quantify the PTM stoichiometry in complex biological samples. This strategy employs a resolvable mass tag to differentiate proteoforms with different numbers of modifications and utilizes liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) techniques to measure PTM stoichiometry at the proteomic level. As a proof-of-concept, we successfully determined the stoichiometry of 197 proteins modified by 4-hydroxynonenal (HNE), a well-characterized lipid-derived electrophile and biomRSC chemical biologyQuantitative profiling of PTM stoichiometry by resolvable mass tags.PMC9627732919531092192570192153301Liu YLi YQuan BWang CChen YQin WfalseQuantitative profiling of PTM stoichiometry by resolvable mass tags.Post-translational modifications (PTMs) play important roles in modulating the biological functions of proteins. Stoichiometry, which quantifies the modification percentage, is a critical factor for any given PTM. In this work, we developed a chemoproteomic strategy called "STO-MS" to systematically quantify the PTM stoichiometry in complex biological samples. This strategy employs a resolvable mass tag to differentiate proteoforms with different numbers of modifications and utilizes liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) techniques to measure PTM stoichiometry at the proteomic level. As a proof-of-concept, we successfully determined the stoichiometry of 197 proteins modified by 4-hydroxynonenal (HNE), a well-characterized lipid-derived electrophile and biom2022-01-01T00:00:00Z2022 Nov2025-04-21T23:35:16.595Z2025-04-05T19:11:21.284ZS-EPMC96277323634922310.1039/d2cb00179a