Differential oxidation of surimi actomyosin by malondialdehyde and heme: spectroscopy and molecular simulation.

Pro-oxidative factors compromise surimi gel quality by inducing protein denaturation and aggregation. This study elucidated the interactions between malondialdehyde (MDA) and hemin with surimi actomyosin through multispectral analysis and molecular dynamics (MD) simulations. The results suggested that MDA and hemin induced actomyosin oxidation by altering protein conformation, surface hydrophobicity, and the microenvironment of aromatic residues, especially under low-pH/high-temperature conditions. The MD results confirmed that MDA weakly interacted with myosin owing to its flexible backbone and limited hydrophobicity (ΔE = +0.24 kcal/mol), whereas hemin forms stable interactions (ΔE = -33.64 kcal/mol), likely due to its central iron atom, rigid porphyrin ring, and polar groups. Under co-exposure, hemin facilitated the relocation of MDA into deeper binding pockets, forming a synergistic network driven by hydrogen bonding, van der Waals forces, and hydrophobic interactions (ΔE = +0.05 kcal/mol for MDA; -28.71 kcal/mol for hemin). These findings provide molecular-level insights into surimi quality deterioration and support strategies to mitigate protein oxidation during processing.