Experimental and computational investigation to elucidate the structure and dynamics of amino acid-based deep...

Deep Eutectic Solvents derived from amino acids are considered environmentally friendly because they are biodegradable, recyclable, and exhibit acceptable levels of toxicity. These solvents have various applications in various fields, such as biocatalysis, electrochemistry, extraction, and pharmaceuticals. Glutamine is an amino acid commonly found in human blood, and glycerol is a conventional solvent with rapid biodegradability. In this study, biodegradable amino acids based deep eutectic solvent (DES) was prepared from the mixture of glutamine and glycerol at a 1:3 (Glu: Gly) molar ratio, and differential scanning calorimetry (DSC) was used to confirm the phase transition. Exothermic and endothermic phase transitions detected at -5.12 °C and 2.83 °C respectively. Moreover, peak broadening due to spectral shifts of functional groups in the FTIR data confirmed the formation of DES, and PCA on the IR data concluded that the DES formation was glutamine-dominated. ¹H NMR experiment was conducted to understand the chemical structure of the DES system. Molecular dynamics (MD) simulation and density functional theory were applied to study the structure and interaction of DES. The radial distribution function from the MD simulation confirmed the existence of three hydrogen bonds that stabilized the complex. Independent gradient model based on Hirshfeld partition (IGMH) analysis visualized the strongest interaction between the carboxylic acid of the glutamine and the alcoholic group of glycerol. Charge transfer analysis identified glycerol as a hydrogen bond donor and glutamine as a hydrogen bond acceptor. The application of our DES system was evaluated by measuring Density, pH and Conductivity. All these extensive insights will contribute to a deeper understanding of other biodegradable amino acid-based DESs and provide a broader approach to DES research.