查看文章

Ionic liquids (ILs) are gaining attention as protein stabilizers and refolding additives. However, varying degrees of success with this approach motivates the need to better understand fundamental IL–protein interactions. A combination of experiment and simulation is used to investigate the thermal unfolding of lysozyme in the presence of two imidazolium-based ILs (1-ethyl-3-methylimidazolium ethylsulfate, [EMIM][EtSO4] and 1-ethyl-3-methylimidazolium diethylphosphate, [EMIM][Et2PO4]). Both ILs reduce lysozyme melting temperature Tm, but more gradually than strong denaturants. [EMIM][Et2PO4] lowers lysozyme Tm more readily than [EMIM][EtSO4], as well as requiring less energy to unfold the protein, as determined by the calorimetric enthalpy ΔH. Intrinsic fluorescence measurements indicate that both ILs bind to tryptophan residues in a dynamic mode, and furthermore, molecular dynamics simulations show …