Molecular simulations explain the exceptional thermal stability, solvent tolerance and solubility of protein-polymer surfactant bioconjugates in ionic liquids.

Proteins complexed electrostatically with polymer surfactants constitute a viscous liquid by themselves, called the solvent-free protein liquid (SFPL). A solution of SFPL in a room temperature ionic liquid (PS-IL) offers the protein hyperthermal stability, higher solubility and greater IL tolerance. A generic understanding of these protein-polymer systems is obtained herein through extensive atomistic molecular dynamics simulations of three different enzymes (lipase A, lysozyme and myoglobin) under various conditions. Along with increased intra-protein hydrogen bonding, the surfactant coating around the proteins imparts greater thermal stability, and also aids in screening protein-IL interactions, endowing them IL tolerance. The reduced surface polarity of the protein-polymer bioconjugate and hydrogen bonding between the ethylene glycol groups of the surfactant and the IL cation contribute to the facile solvation of the protein in its PS-IL form. The results presented here rationalize several experimental observations and will aid in the improved design of such hybrid materials for sustainable catalysis.