Aqueous ionic liquids in comparison with standard co-solutes
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Ionic liquids (ILs) are versatile solvents for a broad range of biotechnological applications. Recent experimental and simulation results highlight the potential benefits of dilute ILs in aqueous solution (aqueous ILs) in order to modify protein and DNA structures systematically. In contrast to a limited number of standard co-solutes like urea, ectoine, trimethylamine-N-oxide (TMAO), or guanidinium chloride, the large amount of possible cation and anion combinations in aqueous ILs can be used to develop tailor-made stabilizers or destabilizers for specific purposes. In this review article, we highlight common principles and differences between aqueous ILs and standard co-solutes with a specific focus on their underlying macromolecular stabilization or destabilization behavior. In combination with statistical thermodynamics theories, we present an efficient framework, which is used to classify structure modification effects consistently. The crucial importance of enthalpic and entropic contributions to the free energy change upon IL-assisted macromolecular unfolding in combination with a complex destabilization mechanism is described in detail. A special focus is also set on aqueous IL-DNA interactions, for which experimental and simulation outcomes are summarized and discussed in the context of previous findings.
KeywordsIonic liquids Proteins DNA Co-solutes Kirkwood-Buff theory
The authors acknowledge helpful discussions with Diddo Diddens, Volker Lesch, Andreas Heuer, Hans-Joachim Galla, Julian Michalowsky, Miriam Kohagen, Frank Uhlig, Johannes Zeman, Maria Fyta, Takeshi Kobayashi, Anand Narayanan Krishnamoorthy, Samantha Micciulla, Martin Grininger, Wilhelm-Maximilian Hützler, Marc-Benjamin Hahn, Tihomir Solomun, Heinz Sturm, Martin Schroer, Christian Schröder, and Christian Holm.
This work was funded by the Deutsche Forschungsgemeinschaft through the Sonderforschungsbereich 716 (SFB 716)
Compliance with ethical standards
Conflict of interest
Ewa Anna Oprzeska-Zingrebe declares that she has no conflicts of interest. Jens Smiatek declares that he has no conflicts of interest.
This article does not contain any studies with human participants or animals performed by any of the authors.
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