Lysozyme Solubility and Conformation in Neat Ionic Liquids and Their Mixtures with Water

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• 作者：Stephen Strassburg ; Harry Bermudez ; David Hoagland
• 刊名：Biomacromolecules
• 出版年：2016
• 出版时间：June 13, 2016
• 年：2016
• 卷：17
• 期：6
• 页码：2233-2239
• 全文大小：340K
• 年卷期：0
• ISSN：1526-4602

文摘

The room temperature solubility of a number of model proteins is assessed for a diverse set of neat ionic liquids (ILs). For two soluble protein–IL pairs, lysozyme in [C₂MIM][EtSO₄] (1-ethyl-3-methylimidazolium ethylsulfate) and in [C_2,4,4,4P][Et₂PO₄] (tributyl(ethyl)phosphonium diethylphosphate), protein solubility and structure at various temperatures are probed by dynamic light scattering (assessing dissolved molecular size), turbidimetry (reflecting degree of solubility), and Fourier transform infrared spectroscopy (uncovering helical secondary structure). As compared to aqueous environments, [C_2,4,4,4P][Et₂PO₄] thermally stabilizes protein size and secondary structure while [C₂MIM][EtSO₄] does the opposite. Lysozyme denatured in [C₂MIM][EtSO₄] does not aggregate, presumably due to an absence of hydrophobic interactions, and the denaturation appears thermally reversible. Both ILs at room temperature are miscible with water in all proportions, but to create the corresponding ternary mixtures with protein, the order of mixing is important. Mixed to avoid additions of water to IL-dissolved protein, stable solutions are obtained with [C₂MIM][EtSO₄] at all solvent compositions. When water is added to IL-rich solutions, liquid–liquid demixing is noted.