engleski

Natural Deep Eutectic Solvents (NADES) as a stabilising medium for nicotinamide coenzymes

Coenzymes are an indispensable part of oxidoreductase-catalyzed reactions, with nicotinamide coenzymes NAD+ and NADH being most frequently present. They have found increasing application in biocatalysis, especially in the reduction of prochiral compounds. When designing such processes, the major drawbacks are the high coenzyme price, its instability in aqueous solution, pH dependence and recyclation.[1] Because coenzymes are known for their labile nature and short-term stability, new and fresh stock solutions need to be prepared prior to the reaction. Therefore, finding a solvent that could simultaneously stabilise both nicotinamide coenzymes in oxidoreductive biocatalytic reactions and minimize their degradation during storage could be of great significance. In the last decade, new natural deep eutectic solvents (NADES) have arisen as a promising tool to shape already green biocatalysis into an even more ecological and sustainable process. NADES are solvents with valuable characteristics such as reduced emissions and toxicity, low volatility, biodegradability, but most importantly easy tunability. Their structural flexibility offers a possibility for rational solvent design to fulfill specific purposes and industrial requests.[2] One of their applications has also been shown for solubilisation and stabilisation of a wide range of biomolecules.[3] In this work, NADES were investigated as a stabilisation medium for nicotinamide coenzymes, NAD+ as an oxidized and NADH as a reduced form. Results showed that coenzymes stabilisation strongly depends on the hydrogen bond donor nature and water content. Cholinium-based NADES containing amide urea as hydrogen bond donor, stabilise both coenzyme forms to a much greater extent than reference buffers. The observed stabilisation effect is significant considering that these two coenzyme forms prefer media with different pH values. Moreover, long term stability of the coenzymes within studied NADES up to 50 days was confirmed. Several approaches were investigated to better understand the coenzyme stabilisation phenomena in NADES by implementing UV/VIS spectroscopy, NMR analysis and molecular dynamics simulations. This discovery can open a new chapter in coenzyme recycling and reuse during continuous biocatalytic reactions and most importantly, it could solve coenzyme storage shortcomings.

deep eutectic solvents ; nicotinamide coenzymes ; molecular dinamics

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