Unraveling the Impact of Diverse Salt Solvent Systems on the Structure and Functionality of Eggshell Membrane Proteins

This study investigated the effects of different solvent systems on the microstructure, roughness, and secondary structure of soluble eggshell membrane proteins (SEPs). The solvent system of CaCl₂/C₂H₅OH/H₂O produced tiny holes on the surface of SEP, and LiBr resulted in the formation of long holes. The saline solution increased the diameter of the protein fiber, the particle size of the solution, and the surface roughness of regenerated SEP films, mainly due to the enhanced intermolecular aggregation and precipitation. Zeta potential measurements indicated salts decreased the negative values and reduced the stability of the SEP solution. The different solutions showed similar circular dichroism waveforms. The peak intensity decreased at the positive and negative peaks, indicating that the triple helix structure of collagen was denatured to different degrees. Besides, the addition of salts decreased the content of α-helices and the β-turns and increased the content of β-sheets and random coils, indicating an increase in the disordered structure of the protein. This study contributes to a deeper understanding of the structural and functional relationships of eggshell membrane proteins, providing a vital basis for developing novel, eco-friendly, and multifunctional protein materials.