Impact of ionic liquid environment on Lysozyme stability

Stability of local tryptophan environment (Trp-environment) in Lysozyme was determined in the presence of water miscible aprotic ionic liquids, i.e., 1-ethyl-3-methylimidazolium, 1-butyl-3-methylimidazolium, 1-octyl-3-methylimidazolium cations and different types of anions such as sulphate and chloride, as the additives in water and buffer. Addition of ionic liquids to the protein solution brings a change in the hydrophobic environment of Trptophan in the protein. The disrupting behaviour of the ionic liquids increases with increase in alkyl chain length and the hydrophobicity of the imidazolium cation. It is observed that more is the hydrophobic nature of the substituent more is the disruption in native Trp environment. On the other hand and in the case of anions, anions follows Hofmeister series (i.e., negative compactness effect of chloride is more than sulfate)