Molecular Structure Changes of Yak Myofibrillar Proteins via Protein Oxidation at Different pH Values
Article
Figures
Metrics
Preview PDF
Reference
Related
Cited by
Materials
Abstract:
Myofibrillar proteins from yak meat were incubated for 24 h in a hydroxyl radical oxidation system with different H2O2 concentrations at various pH values. By analyzing carbonyl, mercapto, secondary structure, tertiary structure, SDS-PAGE separation, and other indicators, the effects of oxidation at different pH values on the molecular structure of yak muscle myofibrillar proteins were investigated. The results show that with the increase of H2O2 concentration at different pH values, the carbonyl content increases from the initial level of 27.2 nmol/mg to 36.44 nmol/mg (5.0), 36.98 nmol/mg (6.0), 33.64 nmol/mg (7.0), and 34.53 nmol/mg (8.0), whereas the surface hydrophobicity increases from 383.64 (5.0), 275.58 (6.0), 245.21 (7.0), and 238.99 to 484.23, 410.92, 306.69, and 291.13, respectively. Moreover, the total mercapto content decreases from the initial level of 92.1 nmol/mg to 80.68 nmol/mg (5.0), 78.72 nmol/mg (6.0), 87.6 nmol/mg (7.0), and 86.28 nmol/mg (8.0). The solubility was reduced by 1.8 times, and the endogenous fluorescence intensity dropped. The proportion of secondary structures decreased. After oxidation, cross-linking was observed within the protein molecules. As the pH value is farther away from the isoelectric point, the increased rate of the carbonyl content was reduced, whereas the decline rate of the sulfhydryl and free amino contents decreased. Meanwhile, the solubility and endogenous fluorescence intensity increased, and the hydrophobicity decreased. Myofibril proteins close to the isoelectric point have more β-pleated sheet structures and fewer α-helix structures. The results demonstrate that myofibrillar proteins have a higher degree of oxidation near the isoelectric point.
