Prediction of Solubility Behavior of Globular Plant Proteins with Hansen Solubility Parameters: A Conformational Study

In this study Hansen solubility parameter (HSP) theory was utilized to discover proper solvent systems that can replace solid denaturants, such as urea or guanidinium chloride, in order to prepare processable plant protein solutions as potential sources of new industrial macromolecules. Soybean proteins, glycinin, and beta-conglycinin were selected, and their structural effects on solubility in different solvent systems and unfolding status were investigated. The results revealed that certain organic solvent systems with HSPs similar to 6 M urea aqueous solution tend to dissolve both proteins, and a high correlation was observed between their solubility and R-a values. Dynamic light scattering and nanodifferential scanning calorimetry of the proteins in selected solvent systems were measured in order to understand denatured status of the proteins in the solvent systems. It was observed that hydrodynamic radii of the both proteins were increased by decreasing the R-a values, and significant denaturation was detected for the solutions with HSPs closer to 6 M urea solutions. Also, the solvent systems with high R-a values revealed gel-like rheological behavior, while HSPs close samples presented shear-thinning behaviors, an indication of extended protein chains. Lastly, HSPs theory can meaningfully predict the ability of different solvents that can dissolve and denature plant proteins.