Preferential Interaction of β-Globulin from Sesame Seeds (Sesamum indicum L.) with Cosolvents Is Accompanied by the Protein Structural Reorganization

The effect of a cosolvent on the structure and stability of a protein depends upon the nature of preferential protein- water, protein-cosolvent or cosolvent-water interactions. The preferential interaction parameters of glycerol, sorbitol and sucrose with β-globulin (from Sesamum indicum L. seeds) were evaluated and the results showed the exclusion of cosolvents and preferential hydration of the protein. Data from fluorescence, circular dichroism (CD) and thermal stability measurements inferred that the preferential hydration had a considerable effect on the structure of protein under native conditions. Such cosolvent-protein interactions bring out a previously unnoticed, but outstanding phenomenon of cosolvent induced structural effects on the protein. This study reveals that these cosolvents interact with β-globulin in such a way that they induce a structural reshuffling to enhance the protein stability, mostly by intensifying intra-molecular hydrophobic interactions.