Role of ionic liquids on stability of bovine serum albumin

Bovine Serum Albumin (BSA) in water and PBS get affected by the introduction of different ionic liquids. The impact of the model ionic liquids, i.e., 1-ethyl-3-methylimidazolium sulfate, 1-ethyl-3-methylimidazolium chloride, and 1-butyl-3-methylimidazolium chloride, on the tryptophan environment (Trp-environment) was determined by using fluorescence technique. The effect of different aprotic ionic liquids with the variations in cations and anions is very much significant. The presence of ionic liquids alters the Trp environment present in BSA, i.e., presence of hydrophobic and longer alkyl chain moieties disrupt the hydrophobic environment of tryptophan in the native BSA structure. Similarly, anions like sulfate and chloride have significant impact. Surprisingly, chloride exerts less disruption towards the Trp-environment compared to sulfate, which violates the Hofmeister series (as per Hofmeister series, sulfate should have more impact on the stability compared to chloride)