Detection and identification of 4-hydroxy-2-nonenal Schiff-base adducts along with products of Michael addition using data-dependent neutral loss-driven MS3 acquisition: method evaluation through an in vitro study on cytochrome c oxidase modifications.

We report a data-dependent neutral-loss-driven MS(3) acquisition to enhance, in addition to abundant Michael adducts, the detection of Schiff-base adducts of proteins and 4-hydroxy-2-nonenal, a reactive end product of lipid peroxidation. In vitro modification of cytochrome c oxidase, a mitochondrial protein complex, was used as a model to evaluate the method. The technique allowed for a confident validation of modification sites and also identified a Schiff-base adduct in subunit Vb of the protein complex.