Effect of Hydroxyl Radical Oxidation on the Structure of Silver Carp Myofibrillar Protein

In this paper,myofibrillar protein from sliver carp were artificial oxidized in a hydroxyl radical-generating systems(the concentration of H₂O₂ were 0.1,1,5,10 and 50 mmol/L,respectively),and the effects of oxidization and the structural characteristics of myofibrillar protein were investigated. The results showed that with the increasing of H₂O₂ concentration at the range of 0~10 mmol/L,the carbonyl contents and di-tyrosine contents increased significantly(P<0.05),and the total thiol group levels and active thiol group levels decreased significantly(P<0.05)when concentration of H₂O₂ was higher than 1 mmol/L.Endogenous fluorescence decreased significantly,surface hydrophobicity increased significantly and particle size distribution moved in the direction of large particle size after oxidization. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis(SDS-PAGE)result showed that hydroxyl radical oxidation could induce the different degrees of cross-linking or aggregation of protein molecules,and the cross-linking mode was mainly disulfide bonds. In addition,the effect on the secondary structure of the protein was that the α-helix was transformed into β-sheet when the concentration of H₂O₂ was 0~1 mmol/L. The β-sheet was transformed into random coil when the concentration of H₂O₂ was 1~50 mmol/L. Amino acid analysis indicated that almost all amino acids were involved in the oxidation process,but the sensitivity of amino acids to hydroxyl radicals was cysteine > alanine > lysine > tyrosine. In conclusion,hydroxyl radical oxidation has changed the structure of myofibrillar proteins.