Representative product-ion mass spectrometric analyses of carnosine-adducted 4-hydroxyalkenal species. Carnosine-4-hydroxyalkenal adducts were prepared by incubating individual 4-hydroxyalkenal species with carnosine at 37°C for 24 hrs as described under “Materials and Methods”. Product-ion ESI-MS analyses of carnosine adducts of 4-hydroxynonenal (4-HNE, Panel A), 4-hydroxyhexenal (4-HHE, Panel C), and 4-hydroxynondienal (4-HNDE, Panel D) were performed on a QqQ mass spectrometer as described under “Materials and Methods”. The fragmentation pattern of protonated 4-HNE-carnosine adduct was proposed (Panel B).