Preliminary Exploration on the Regulatory Mechanism of Ionic Strength on Conformation and Hydration of Silver Carp Myosin

Myosin is abundant in fish muscle tissue and plays a crucial role in gel quality of fish products. The gel forming ability of myosin is related to its solubility and conformation in ionic solution. This study investigated the regulation of NaCl concentrations (0.0~1.0 mol/L) on the solubility of silver carp (Hypophthalmichthys molitrix) myosin from the perspectives of conformation and hydration behavior. Results revealed that proper ionic strength (0.3~0.8 mol/L) significantly improved the solubility of myosin and reduced the average protein size (p < 0.05). Atomic force microscopy (AFM) observation also confirmed a decrease in the size of myosin aggregates. Increasing ionic strength induced the extending of the myosin structure and exposure of aromatic residues. These conformational changes enhanced protein–water interactions through hydrogen bonds, manifested as the formation of hydration layers. Molecular dynamics (MD) simulations also confirmed that appropriate ionic strength increased the number of hydrogen bonds between myosin and water molecules. In conclusion, proper ionic strength (0.3~0.8 mol/L)-induced exposure of polar groups in myosin enhances its hydration capacity, thereby improving solubility.