Impact of pH and NaCl on the molecular conformation of myosin and myosin microgel and underlying mechanism: A comprehensive study using spectroscopy and molecular dynamics simulation

The conformation of myosin in its natural and denatured state can be changed by adjusting the pH and NaCl concentration. Raman spectroscopy, endogenous fluorescence, scanning electron microscopy, and molecular dynamics (MD) were used to observe the molecular conformational changes of tilapia myosin and myosin microgel (MM). When the NaCl concentration was 0.6 mol/L and the pH was 7.0, myosin and MM were in a fibrillated state, contained a high alpha-helix content, exhibited the highest intensity of endogenous fluorescence, and showed a loose conformation (Rgmyosin: 3.32 +/- 0.06 nm, RgMM: 3.11 +/- 0. 01 nm), and high solvent-accessibility surface area (SASA) (SASAmyosin: 406 +/- 4 nm2; SASAMM: 378 +/- 3 nm2) with high secondary structure stability. The pH and NaCl affected the SASA, hydrogen bonding number, and charge of myosin and MM, leading to secondary structure and conformational changes. Compared to NaCl, the pH exhibited a greater effect on the conformation of myosin and MM, and MM improved the stability of the protein. In conclusion, this study clarified the above mentioned conformational changes in proteins at the molecular level, which may facilitate the development of myosin in food processing.