Direct Correlation Between the H/D Exchange Reaction and Conformational Changes of the Cation in Imidazolium-Based Ionic Liquid–D2O Mixtures

Protein Cryoprotectant Ability of the Aqueous Zwitterionic Solution

Protein cryopreservation is important for the long-term storage of unstable proteins. Recently, we found that N-acetylglucosaminyltransferase-V (GnT-V) can be cryopreserved in a deep freezer without temperature control using a dilute binary aqueous solution of 3-(1-(2-(2-methoxyethoxy)ethyl)imidazol-3-io)butane-1-carboxylate (OE2imC3C) [10 wt %, mole fraction of solute (x) = 7.75 × 10-3], an artificial zwitterion. However, it is unclear which solvent properties are required in these media to preserve unstable proteins, such as GnT-V. In this study, we investigated the melting phenomena and solution structure of dilute binary aqueous OE2imC3C solutions [x = 0-2.96 × 10-2 (0-30 wt %)] using differential scanning calorimetry (DSC) and Raman and Fourier transform infrared (FTIR) spectroscopies combined with molecular dynamics (MD) simulation to compare the cryoprotectant ability of OE2imC3C with two general cryoprotectants (CPAs), glycerol and dimethyl sulfoxide. DSC results indicated that aqueous OE2imC3C solutions can be melted at lower temperatures with less energy than the control CPA solution, with increasing x, primarily due to OE2imC3C having a higher content of unfrozen water molecules. Moreover, Raman and FTIR results showed that the high content of unfrozen water molecules in aqueous OE2imC3C solutions was due to the hydration around the ionic parts (the COO- group and imidazolium ring) and the OCH2CH2O segment. In addition, the MD simulation results showed that there were fewer structured water molecules around the OCH2CH2O segment than the hydration water molecules around the ionic parts. These solvent properties suggest that dilute aqueous OE2imC3C solutions are effective in preventing freezing, even in a deep freezer. Therefore, this medium has the potential to act as a novel cryoprotectant for proteins in biotechnology and biomedical fields.

Targeted modifications in ionic liquids - from understanding to design

Ionic liquids are extremely versatile and continue to find new applications in academia as well as industry. This versatility is rooted in the manifold of possible ion types, ion combinations, and ion variations. However, to fully exploit this versatility, it is imperative to understand how the properties of ionic liquids arise from their constituents. In this work, we discuss targeted modifications as a powerful tool to provide understanding and to enable design. A 'targeted modification' is a deliberate change in the structure of an ionic liquid. This includes chemical changes in an experiment as well as changes to the parameterisation in a computer simulation. In any case, such a change must be purposeful to isolate what is of interest, studying, as far as is possible, only one concept at a time. The concepts can then be used as design elements. However, it is often found that several design elements interact with each other - sometimes synergistically, and other times antagonistically. Targeted modifications are a systematic way of navigating these overlaps. We hope this paper shows that understanding ionic liquids requires experimentalists and theoreticians to join forces and provides a tool to tackle the difficult transition from understanding to design.

Proton-deuterium exchange of acetone catalyzed in imidazolium-based ionic liquid-D2O mixtures

The reaction of the proton-deuterium exchange of acetone in imidazolium-based ionic liquid (IL)-deuterium oxide mixtures was studied in detail via NMR spectroscopy. Certain ILs exhibit considerable catalytic properties and contribute to the course of reaction up to the complete deuteration. The efficiency of deuterium exchange crucially depends on the features of ILs; the type of anion and chain length of cation. The linear secondary isotope effects on the NMR chemical shifts of the 13C atoms in acetone were observed depending on the deuteration level of the molecule.