Variations in oxidation profiles of myofibrillar protein from silver carp (Hypophthalmichthys molitrix) by frozen storage and hydroxyl radicals: A proteomic insight

Hypothesizing that myofibrillar proteins (MPs) exhibit different oxidation susceptibility, this study compared the structural disintegration and oxidation profiles of fish MPs induced by frozen storage and hydroxyl radicals. Results show that both treatments generated similar levels of carbonyls (∼3.0 nmol/mg) and thiols (∼4.5 mol/10 5  g), while frozen storage caused greater disruption of secondary and tertiary structures than hydroxyl radicals. Proteomic profiling revealed higher generic oxidation levels in myosin heavy chains (MHC, ∼3 %) compared to light chains (<1 %) and actin (∼2 %). Notably, MPs oxidation varied among MHC isoforms: MHC3 had the highest oxidized peptides numbers (129), while MHC2 showed the highest overall oxidation level (3.39 %). Moreover, MPs exhibited distinct oxidation patterns: lipoxidation dominated after frozen storage, while hydroxyl radicals primarily induced mono-oxidation. These findings revealed the site-specific and condition-dependent nature of MPs oxidation, providing critical insights for selecting and designing in vitro oxidizing models to simulate real-world oxidation.