Chapter Six: Natural deep eutectic solvents: Hypothesis for their possible roles in cellular functions and interaction with membranes and other organized biological systems.

The involvement of natural deep eutectic solvents (NADES) in biological processes has been speculated but experimental evidence based on their observation in cells and biochemical reactions is still largely missing. Nevertheless, a sum of observations and analogies between NADES physical-chemical properties and those of peculiar cellular environments allows raising interesting hypothesis on the role they could play. To contribute to the current thinking on NADES in biological systems, an overview of these unusual liquid media is first presented with a special focus on how their occurrence in Nature (animal and plant) and hypothetical roles in cell metabolism were supported by experimental approaches. Then, a discussion pointing out the diversity of membranes formation and structures, describes, while challenging the readers, how NADES may be related with membrane systems. The occurrence of NADES in the cell and their possible interaction with highly organized intracellular structures and membrane-less organelles is also discussed. Observations already made with NADES metabolites in cells allow discussing the possible roles and effects of NADES on cell metabolism in connection with membranes or subcellular assemblies. Finally, suggestions for further investigations regarding the occurrence and the contribution of NADES in the regulation of cellular functions are proposed. [ABSTRACT FROM AUTHOR]