| dc.description.abstract | In protein science, ionic liquids (ILs) have a great influence on the structure, stability, and functional groups of protein. In addition, ILs has received extensive attention in protein assays due to their novel and highly efficient reaction medium as well as also active participants in different biological processes. The present thesis explains the role of ILs (particularly imidazolium and cholinium based) on the protein folding/unfolding studies. Therefore, in this work, it has been explored the structure, stability and activity of stem bromelain (BM) in the presence of different ILs such as imidazolium and choline-based, namely: 1-butyl-3-methylimidazolium chloride ([Bmim][Cl]), 1-butyl-3-methylimidazolium bromide ([Bmim][Br]), 1-butyl-3-methylimidazolium iodide ([Bmim][I]), 1-butyl-3-methylimidazolium hydrogen sulphate ([Bmim][HSO₄]), 1-butyl-3-methylimidazolium acetate ([Bmim][CH₃COO]), 1-butyl-3-methylimidazolium nitrate ([Bmim][NO₃]), choline chloride ([Ch][Cl]), choline acetate ([Ch][Ac]), choline dihydrogen phosphate ([Ch][Dhp]), choline bitartrate ([Ch][Bit]), choline iodide ([Ch][I]) and choline hydroxide ([Ch][OH]) by using various spectroscopic and dynamic light scattering (DLS) measurement techniques. All of these imidazolium based ILs acted as destabilizer for the native structure of BM except concentrations of (such as 0.01 and 0.05 M). Evidently, the stability of series of Hofmeister ions are found to be in the trend of HSO₄‾ > CH₃COO‾ > NO₃‾ > C1‾ > Br‾ > I‾. In the case of choline based ILs the ([Ch][Cl]) is the best stabilizer, whereas ([Ch][OH]) is the strongest destabilizer among all studied ILs for BM structure. The overall stability order of BM in the presence of choline based ILs follow the trend: [Cl] > [Ac] > [Dhp] > [I]) > [Bit] > [OH]. Finally, it has been concluded that the stability of protiens is dependent on the nature of the ILs and their concentrations. In addition to above, the thermophysical properties such as density (ρ), sound velocity (u), viscosity (η) and refractive indice (nD) of binary mixtures of ammonium based ILs, namely tetrapropylammonium hydroxide (TPAOH), tetraethylammonium hydroxide (TEAOH) and tetrabutylammonium hydroxide (TBAOH) with N,N-dimethylacetamide (DMA) over the whole range of composition at different temperatures from 25 to 40 °C under atmospheric pressure have been also reported. The derived properties such as deviation in isentropic compressibilities (ΔKₛ), excess molar volumes (Vᴱ), deviation in viscosities (Δη) and deviation in refractive indices (ΔnD) were calculated from experimental values and correlated by Redlich-Kister polynomial type equations. It has been observed the strength of intermolecular interactions such as ion-ion pair interactions, hydrogen bonding and induced dipole interactions between the ions of ammonium-based ILs with DMA. Futhermore, the solute-solvent interactions of binary mixtures containing 1-methyl-1-propyl pyrrolidinium tetrafluoroborate ([MPpyr][BF₄]) with water, alcohols (methanol and ethanol) at various temperatures from 25 to 40 °C under atmospheric pressure have been also studied. Derived properties such as apparent molar volume (Vᵩ), limiting apparent molar volumes (Vᵩ⁰), the limiting apparent molar expansibility (Eᵩ⁰), and thermal expansion coefficients (α ₚ) were evaluated from experimental density data. The parameters correlated using to the Redlich−Mayer type equation. The obtained results were discussed in terms of the effect of temperature as well as concentration on specific solute-solvent interactions that prevail in the presence of IL solution. | en_US |
