Interaction of bovine serum albumi with two alkylimidazolium-based ionic liquids investigated by microcalorimetry and circular dichroism

Abstract

The interactions of bovine serum albumin (BSA) with two alkylimidazolium-based ionic liquids, 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim]BF 4 ) and 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]PF 6 ), in buffer solutions at pH 7.0 were investigated by isothermal titration calorimetry (ITC) and circular dichroism (CD). CD spectra showed that the two ionic liquids changed the secondary structure of BSA. Data process was based on the supposition that there were several independent types of binding sites on each BSA molecule for the two ligand molecules. The results obtained by using this supposition combined with Langmuir adsorption model showed that there were two types of such binding sites. One was the high affinity binding site, and the other was the low affinity binding site. The binding constants, changes in enthalpy, entropy and Gibbs free energy for the two types of binding were obtained, which showed that the two types of binding were driven by a favorable entropy increase. Furthermore, for either the ionic liquids, the number of the high affinity binding sites is much smaller than that of the low affinity ones. These results were interpreted with the molecular structure of BSA and the different substituent groups on imidazole ring of the two ionic liquid molecules.

Interaction of ionic liquids with human serum albumin in the view of bioconcentration: a preliminary study

“…However, our study, which including a relatively broad spectrum of imidazolium cations, clearly revealed the higher affinity of longchain ILs to HSA, and hence, their binding at even lower IL concentration might be related also to interaction with the hydrophobic domains (IIA and IIIA) of HSA. The fact that ILs interact with the protein through both electrostatic and hydrophobic interactions has been confirmed by other studies (Zhang et al 2018;Geng et al 2009Geng et al , 2010Mester et al 2010;Pei et al 2012;Yan et al 2012;Cao et al 2014;Wang et al 2012;Zhu et al 2011;Singh et al 2012;Bharmoria et al 2014).…”

Unprecedented Improvement in the Stability of Hemoglobin in the Presence of Promising Green Solvent 1-Allyl-3-methylimidazolium Chloride

“…There are enough evidences in literature which conclude that 4 the interaction between protein and IL depends on the protein as well as on the cations and anions present in the ILs. [19][20][21][22][23] Studies have shown ammonium-based ILs to act as better stabilizing agent for proteins as compared to imidazolium-based ILs. 24 Our research group has out carried protein stability studies in both ammonium and imidazolium-based ILs.…”

“…These investigations suggest that there is no fixed rule which can predict the behavior of protein in ILs. There is enough evidence in the literature that concludes that the interaction between a protein and IL depends on the protein as well as on the cations and anions present in the ILs. − …”

The Overriding Roles of Concentration and Hydrophobic Effect on Structure and Stability of Heme Protein Induced by Imidazolium-Based Ionic Liquids

“…Generally, several ILs are proved to be stabilizers for the enzymes and proteins, in some cases even up to 100 °C, while in some cases denaturation with loss of enzyme activity. Moreover, ILs having imidazolium cations have earned special attention in the field of protein stabilities. − A study by Yan et al on the interaction of [C 4 mim]­[Br] and [C 8 mim]­[Br] with β-casein micelles shows that partitioning of IL molecules in different locations of β-casein micelles was dependent upon concentration and chain length of the IL.…”