A Comprehensive Experimental Study to Understand the Hofmeister Series of Anions of Aqueous Imidazolium-Based Ionic Liquids on Glycine Peptides

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• 作者：Varadhi Govinda ; Pannuru Venkatesu
• 刊名：Industrial & Engineering Chemistry Research
• 出版年：2014
• 出版时间：December 17, 2014
• 年：2014
• 卷：53
• 期：50
• 页码：19628-19642
• 全文大小：745K
• ISSN：1520-5045

文摘

The solubility and stability of biomolecules may be influenced by the addition of cosolvents. Ionic liquids (ILs) have emerged as novel cosolvents for widespread applications in biotechnology and industrial processes. In the present study, we report the solubilities and apparent transfer free energy (螖G_tr^{鈥?/sup>) values for zwitterions containing glycine peptides (GPs) such as glycine (Gly), diglycine (Gly₂), triglycine (Gly₃), tetraglycine (Gly₄), and cyclicglycylglycine (c(GG)) from water to aqueous solutions of imidazolium-based ILs at 25 掳C and atmospheric pressure. ILs used here have different anions such as chloride (Cl鈥?/sup>), bromide(Br鈥?/sup>), hydrogen sulfate (HSO₄鈥?/sup>), acetate (CH₃COO鈥?/sup>), and thiocyanate (SCN鈥?/sup>) and a common 1-butyl-3-methylimidazolium cation [Bmim]+. The 螖G_tr鈥?/sup> values of GPs from water to aqueous IL solutions have been obtained from the solubilities, which are determined from density (蟻) measurements as a function of IL concentration at 25 掳C. Further, we have calculated the salting constant (k) from the Setschenow equation, and the values have been analyzed with salting-out/salting-in effects. The experimental 螖G_tr鈥?/sup> data allowed the calculation of the transfer free energy contributions (螖g_tr鈥?/sup>)of the peptide backbone unit (鈭?i>CH₂C鈺?i>ONH鈭? from water to aqueous ILs. The effects of anions of ILs on GPs have been analyzed through solubilities, stabilities, and 螖G_tr鈥?/sup> values to obtain a usual understanding of the Hofmeister series. The results are discussed in terms of solute鈥搒olute and solute鈥搒olvent interactions in the aqueous IL solution.}