Insight into Ionic Strength-Induced Solubilization of Myofibrillar Proteins from Silver Carp ( Hypophthalmichthys molitrix ): Structural Changes and 4D Label-Free Proteomics Analysis.

In this study, changes in the physical, structural, and assembly characteristics of silver carp myofibrillar proteins (MPs) at different ionic strength ( I ) values were investigated. Moreover, the differential proteomic profile of soluble MPs was analyzed using 4D proteomics based on timsTOF Pro mass spectrometry. Solubility of MPs significantly increased at high I (>0.3), and the increase in I enhanced the apparent viscosity, fluorescence intensity, surface hydrophobicity, and α-helix content of MPs solution. Particle size and sodium dodecyl sulfate-polyacrylamide gel electrophoresis patterns also supported the solubility profiles. Transmission electron microscopy and atomic force microscopy observations revealed the morphological assembly and disassembly of MPs under different I conditions. Finally, proteomic analysis revealed the evolution law of salt-induced solubilization of MPs and the critical molecular characteristics in different I environments. The number of differentially abundant proteins (DAPs) decreased with the increase of I , and most DAPs related to the muscle filament sliding, contraction and assembly, actinin binding, and actin filament binding. The soluble abundance of myosin and some structural proteins was dependent on I , and structural proteins in the Z-disk and M-band might contribute to the solubilization of myosin. Our findings provide insightful information about the impact of common I on the solubility pattern of MPs from freshwater fish.