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Michael addition is an important reaction to form C–C bonds. Different hydrolases (e.g., lipases, proteases, and D-aminoacylase) have been reported to catalyze C–C forming reactions, but the reaction mechanism is not entirely clear. This study examined several model Michael reactions catalyzed by lipases and amino acids in various solvents, and found that “‘water-like”’ functionalized ionic liquids (ILs) increased the reaction yield to 35-55% from 30% in triglyme and 17% in [BMIM][Tf2N]. Interestingly, tertiary amides as solvents remarkably increased the reaction yield (to up to 65–85%) and enantioselectivity (up to 71–84% ee) when catalyzed by porcine pancreatic lipase (PPL). Our experimental, spectroscopic, and computational studies discovered that the lipase catalysis can be attributed to basic amino acid residues as the catalysts to promote Michael addition, especially when tertiary amide solvents partially unfold the protein and expose its basic amino acid residues. 

Biomolecules have been thoroughly investigated in a multitude of solvents historically in order to accentuate or modulate their superlative properties in an array of applications. Ionic liquids have been extensively explored over the last two decades as potential replacements for traditional organic solvents, however, they are sometimes associated with a number of limitations primarily related to cost, convenience, accessibility, and/or sustainability. One potential solvent which is gaining considerable traction in recent years is the so-called deep eutectic solvent which holds a number of striking advantages, including biodegradability, inherently low toxicity, and a facile, low-cost, and solventless preparation from widely available natural feedstocks. In this review, we highlight recent progress and insights into biomolecular behavior within deep eutectic solvent-containing systems, including discussions of their demonstrated utility and prospects for the biostabilization of proteins and nucleic acids, free enzyme and whole-cell biocatalysis, various extraction processes ( e.g. , aqueous biphasic systems, nanosupported separations), drug solubilization, lignocellulose biomass treatment, and targeted therapeutic drug delivery. All indications point to the likelihood that these emerging solvents have the capacity to satisfy the requirements of environmental responsibility while unlocking biomolecular proficiency in established biomedical and biotechnological pursuits as well as a number of academic and industrial ventures not yet explored. 

A liquid–liquid transition (LLT) is a transformation from one liquid to another through a first-order transition. The LLT is fundamental to the understanding of the liquid state and has been reported in a few materials such as silicon, phosphorus, triphenyl phosphite, and water. Furthermore, it has been suggested that the unique properties of materials such as water, which is critical for life on the planet, are linked to the existence of the LLT. However, the experimental evidence for the existence of an LLT in many molecular liquids remains controversial, due to the prevalence and high propensity of the materials to crystallize. Here, we show evidence of an LLT in a glass-forming trihexyltetradecylphosphonium borohydride ionic liquid that shows no tendency to crystallize under normal laboratory conditions. We observe a step-like increase in the static dielectric permittivity at the transition. Furthermore, the sizes of nonpolar local domains and ion-coordination numbers deduced from wide-angle X-ray scattering also change abruptly at the LLT. We independently corroborate these changes in local organization using Raman spectroscopy. The experimental access to the evolution of local order and structural dynamics across a liquid–liquid transition opens up unprecedented possibilities to understand the nature of the liquid state.