Insight Into the Effect of Carnosine on the Dispersibility of Myosin Under a Low-salt Condition and its Mechanism

In this study, carnosine (0‒0.20%, w/v) was introduced to improve the dispersibility of myosin under a low-salt condition (0.1 M NaCl). The underlying dispersion mechanism was investigated. Carnosine has positive effects on the dispersibility of myosin, as evidenced by the significantly improved solubility and turbidity. After the addition of carnosine, the average particle size in each sample remarkably decreased, and the mole mass of the aggregates decreased from 6.74 × 10 7  g/mol to 4.00 × 10 7  g/mol as the carnosine increased from 0.10 to 0.20%. Changes in protein secondary structure, ζ-potential, and ITC (Isothermal titration calorimetry) results indicated that electrostatic interaction is the main force between myosin and carnosine. Moreover, carnosine may hinder the formation of large aggregates by affecting the structure and charge distribution of the myosin tail when carnosine was ≤ 0.10%. However, excess carnosine (˃ 0.10%) had a negative effect on the long-term stability of the protein solution. Turbiscan stability index, visual appearance, and hydrophobicity analyses showed that the instability of the system was possibly due to increase in the hydrophobicity of myosin head after excess carnosine was applied. Our research may contribute to the improvement of the functional properties of myosin under low-salt condition and regulation of protein behavior. Graphical Abstract