Fig. 1. (a) A representation of the lectin probe attached to a target glycan and oxidizing the underlying polypeptide scaffold. The Fe(iii)-modified lectin probes were the cell supernatant and allowed to interact with the glycan target. Hydroxyl radicals were produced at the metal site creating a concentration of radicals that oxidize the proteins in proximity. The membrane proteins are isolated and analyzed by LC-MS. Oxidized proteins are identified and quantified. (b) The modification involved the introduction of the azido group into a primary amine on lysine followed by conjugation of DBCO-FeBABE to the lectin via copper-free “click” chemistry.