Modifying interprotein interactions for controlling heat-induced protein gelation
Sugam Kumar, Debasish Saha, Vinod K. Aswal
Abstract
Globular proteins undergo heat-induced denaturation and eventually gelation at significantly elevated temperatures. The present study provides pathways to control temperature-driven protein gelation, having potential applications in a wide range of fields, from medicine to cosmetics to the food industry. The sol-gel transitions have been directed via modifying interprotein (electrostatic and hydrophobic) interactions by complexation of protein with amphiphiles. The heat-induced gelation of bovine serum albumin protein (anionic) is prevented in the presence of anionic sodium dodecyl sulfate (SDS) surfactant without significantly altering its native conformation. The specific binding of SDS monomers on the oppositely charged sites of protein increases the electrostatic repulsion between protein molecules, thereby suppressing the protein gelation. On the other hand, incorporating nonionic decaoxyethylene $n\ensuremath{-}\mathrm{dodecylether}$ (${\mathrm{C}}_{12}{\mathrm{E}}_{10}$) surfactant along with ionic surfactant reverses this scenario, and the solution state of the bovine serum albumin-SDS system undergoes gelation. The preferential binding of SDS with ${\mathrm{C}}_{12}{\mathrm{E}}_{10}$ nonionic surfactant forms detached mixed micelles, resulting in the release of the SDS monomers from protein, hence reverting the SDS-induced prevention of protein gelation. The results are counterintuitive and explained based on the interplay of hydrophobic and electrostatic interactions among protein molecules, as probed by small-angle neutron scattering, dynamic light scattering, and rheology.