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)

Impact of imidazolium-based ionic liquids on the structure and stability of lysozyme

<p>Various types of water-miscible aprotic ionic liquids (ILs) with different cations (1-ethyl-3-methylimidazolium, 1-butyl-3-methylimidazolium, 1-octyl-3-methylimidazolium) and anions (ethylsulfate and chloride) were used as co-solvents to investigate the stability of lysozyme. Different techniques such as fluorescence, thermal absorption, and circular dichroism (CD) spectroscopy have been used for the study. Fluorescence results reveal that the addition of ILs (1-ethyl-3-methylimidazolium ethyl sulfate and 1-ethyl-3-methylimidazolium) increases the hydrophobicity around the tryptophan environment in lysozyme. CD analysis and temperature-dependent studies were done to investigate the stability of the protein. From the CD analysis, it was observed that the ILs keep the native structure of protein intact. Thermal denaturation studies depicted that the melting temperature of the protein increased in the presence of ILs (1-ethyl-3-methylimidazolium ethyl sulfate and 1-ethyl-3-methylimidazolium), which indicates the stabilization of the protein.</p